10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

 _____________________________________________

FORM 10-Q

 ____________________________________________

(Mark One)
☒	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2023

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                      to                     

Commission file number 001-35714

_____________________________________________ 

MPLX LP

(Exact name of registrant as specified in its charter)

 _____________________________________________

	Delaware	27-0005456
(State or other jurisdiction of incorporation or organization)		(I.R.S. Employer Identification No.)

200 E. Hardin Street,	Findlay,	Ohio	45840
(Address of principal executive offices)			(Zip code)

(419) 421-2414

(Registrant’s telephone number, including area code)

 _____________________________________________

Securities Registered pursuant to Section 12(b) of the Act
Title of each class	Trading symbol(s)	Name of each exchange on which registered
Common Units Representing Limited Partnership Interests	MPLX	New York Stock Exchange

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes  x     No  ¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files.) Yes  x    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer x Accelerated filer ☐ Non-accelerated filer ☐

Smaller reporting company ☐ Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act) Yes  ☐    No  x

MPLX LP had 1,001,217,044 common units outstanding as of October 27, 2023.

Table of Contents

		Page
PART I – FINANCIAL INFORMATION
Item 1.	Financial Statements:
	Consolidated Statements of Income (Unaudited)	3
	Consolidated Statements of Comprehensive Income (Unaudited)	4
	Consolidated Balance Sheets (Unaudited)	5
	Consolidated Statements of Cash Flows (Unaudited)	6
	Consolidated Statements of Equity and Series A Preferred Units (Unaudited)	7
	Notes to Consolidated Financial Statements (Unaudited)	8
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	25
Item 3.	Quantitative and Qualitative Disclosures about Market Risk	45
Item 4.	Controls and Procedures	46
PART II – OTHER INFORMATION
Item 1.	Legal Proceedings	47
Item 1A.	Risk Factors	47
Item 5.	Other Information	48
Item 6.	Exhibits	49
	Signatures	50

Unless otherwise stated or the context otherwise indicates, all references in this Form 10-Q to “MPLX LP,” “MPLX,” “the Partnership,” “we,” “our,” “us,” or like terms refer to MPLX LP and its consolidated subsidiaries. References to our sponsor and customer, “MPC,” refer collectively to Marathon Petroleum Corporation and its subsidiaries, other than the Partnership.

1

Glossary of Terms

The abbreviations, acronyms and industry technology used in this report are defined as follows:

ASC	Accounting Standards Codification
ASU	Accounting Standards Update
Barrel	One stock tank barrel, or 42 U.S. gallons of liquid volume, used in reference to crude oil or other liquid hydrocarbons
DCF (a non-GAAP financial measure)	Distributable Cash Flow
EBITDA (a non-GAAP financial measure)	Earnings Before Interest, Taxes, Depreciation and Amortization
FASB	Financial Accounting Standards Board
FCF (a non-GAAP financial measure)	Free Cash Flow
GAAP	Accounting principles generally accepted in the United States of America
G&P	Gathering and Processing segment
L&S	Logistics and Storage segment
mbpd	Thousand barrels per day
MMBtu	One million British thermal units, an energy measurement
MMcf/d	One million cubic feet of natural gas per day
NGL	Natural gas liquids, such as ethane, propane, butanes and natural gasoline
SEC	U.S. Securities and Exchange Commission
SOFR	Secured Overnight Financing Rate
VIE	Variable interest entity

2

Part I—Financial Information

Item 1. Financial Statements

MPLX LP

Consolidated Statements of Income (Unaudited)

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions, except per unit data)	2023		2022		2023		2022
Revenues and other income:
Service revenue	$	641	$	627	$	1,881	$	1,758
Service revenue - related parties	1,038		948		2,962		2,801
Service revenue - product related	75		83		214		324
Rental income	61		75		181		268
Rental income - related parties	207		201		612		564
Product sales	478		617		1,274		1,812
Product sales - related parties	51		46		155		142
Sales-type lease revenue	34		28		101		28
Sales-type lease revenue - related parties	129		118		379		343
Income from equity method investments	159		125		438		335
Other income	7		505		28		494
Other income - related parties	32		28		90		82
Total revenues and other income	2,912		3,401		8,315		8,951
Costs and expenses:
Cost of revenues (excludes items below)	367		371		1,023		981
Purchased product costs	474		540		1,234		1,670
Rental cost of sales	20		22		60		101
Rental cost of sales - related parties	8		10		24		44
Purchases - related parties	442		364		1,160		1,034
Depreciation and amortization	301		302		907		925
General and administrative expenses	102		88		280		248
Other taxes	44		30		102		97
Total costs and expenses	1,758		1,727		4,790		5,100
Income from operations	1,154		1,674		3,525		3,851
Related-party interest and other financial costs	—		—		—		5
Interest expense, net of amounts capitalized	223		217		673		627
Other financial costs, net	2		19		28		59
Income before income taxes	929		1,438		2,824		3,160
Provision for income taxes	1		1		2		6
Net income	928		1,437		2,822		3,154
Less: Net income attributable to noncontrolling interests	10		9		28		26
Net income attributable to MPLX LP	918		1,428		2,794		3,128
Less: Series A preferred unitholders interest in net income	25		23		71		65
Less: Series B preferred unitholders interest in net income	—		10		5		31
Limited partners' interest in net income attributable to MPLX LP	$	893	$	1,395	$	2,718	$	3,032
Per Unit Data (See Note 6)
Net income attributable to MPLX LP per limited partner unit:
Common - basic	$	0.89	$	1.36	$	2.70	$	2.97
Common - diluted	$	0.89	$	1.36	$	2.70	$	2.97
Weighted average limited partner units outstanding:
Common - basic	1,001		1,010		1,001		1,012
Common - diluted	1,001		1,011		1,001		1,013

The accompanying notes are an integral part of these consolidated financial statements.

3

MPLX LP

Consolidated Statements of Comprehensive Income (Unaudited)

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Net income	$	928	$	1,437	$	2,822	$	3,154
Other comprehensive income, net of tax:
Remeasurements of pension and other postretirement benefits related to equity method investments, net of tax	—		—		4		9
Comprehensive income	928		1,437		2,826		3,163
Less comprehensive income attributable to:
Noncontrolling interests	10		9		28		26
Comprehensive income attributable to MPLX LP	$	918	$	1,428	$	2,798	$	3,137

The accompanying notes are an integral part of these consolidated financial statements.

4

MPLX LP

Consolidated Balance Sheets (Unaudited)

 

(In millions)	September 30, 2023		December 31, 2022
Assets
Cash and cash equivalents	$	960	$	238
Receivables, net	833		737
Current assets - related parties	759		729
Inventories	154		148
Other current assets	30		53
Total current assets	2,736		1,905
Equity method investments	4,099		4,095
Property, plant and equipment, net	18,620		18,848
Intangibles, net	609		705
Goodwill	7,645		7,645
Right of use assets, net	271		283
Noncurrent assets - related parties	1,174		1,225
Other noncurrent assets	966		959
Total assets	36,120		35,665
Liabilities
Accounts payable	132		224
Accrued liabilities	332		269
Current liabilities - related parties	387		343
Accrued property, plant and equipment	140		128
Long-term debt due within one year	1		988
Accrued interest payable	187		237
Operating lease liabilities	48		46
Other current liabilities	172		166
Total current liabilities	1,399		2,401
Long-term deferred revenue	295		219
Long-term liabilities - related parties	343		338
Long-term debt	20,417		18,808
Deferred income taxes	12		13
Long-term operating lease liabilities	219		230
Other long-term liabilities	119		142
Total liabilities	22,804		22,151
Commitments and contingencies (see Note 15)
Series A preferred units (30 million and 30 million units issued and outstanding)	970		968
Equity
Common unitholders - public (354 million and 354 million units issued and outstanding)	8,533		8,413
Common unitholders - MPC (647 million and 647 million units issued and outstanding)	3,581		3,293
Series B preferred units (0 million and 0.6 million units issued and outstanding)	—		611
Accumulated other comprehensive loss	(4)		(8)
Total MPLX LP partners’ capital	12,110		12,309
Noncontrolling interests	236		237
Total equity	12,346		12,546
Total liabilities, preferred units and equity	$	36,120	$	35,665

The accompanying notes are an integral part of these consolidated financial statements.

5

MPLX LP

Consolidated Statements of Cash Flows (Unaudited)

	Nine Months Ended  September 30,
(In millions)	2023		2022
Operating activities:
Net income	$	2,822	$	3,154
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs	42		55
Depreciation and amortization	907		925
Deferred income taxes	(1)		4
Gain on sales-type leases	—		(509)
(Gain)/loss on disposal of assets	(15)		23
Income from equity method investments	(438)		(335)
Distributions from unconsolidated affiliates	526		405
Change in fair value of derivatives	(3)		(62)
Changes in:
Receivables	(31)		(219)
Inventories	(15)		(7)
Accounts payable and accrued liabilities	(56)		49
Assets/liabilities - related parties	89		52
Right of use assets/operating lease liabilities	4		1
Deferred revenue	65		64
All other, net	12		51
Net cash provided by operating activities	3,908		3,651
Investing activities:
Additions to property, plant and equipment	(662)		(535)
Acquisitions, net of cash acquired	—		(28)
Disposal of assets	25		74
Investments in unconsolidated affiliates	(90)		(198)
Distributions from unconsolidated affiliates - return of capital	—		11
Net cash used in investing activities	(727)		(676)
Financing activities:
Long-term debt borrowings	1,589		3,379
Long-term debt repayments	(1,001)		(2,202)
Related party debt borrowings	—		2,824
Related party debt repayments	—		(4,274)
Debt issuance costs	(15)		(29)
Unit repurchases	—		(315)
Redemption of Series B preferred units	(600)		—
Distributions to noncontrolling interests	(30)		(29)
Distributions to Series A preferred unitholders	(69)		(63)
Distributions to Series B preferred unitholders	(21)		(41)
Distributions to unitholders and general partner	(2,329)		(2,144)
Contributions from MPC	20		30
All other, net	(3)		(3)
Net cash used in financing activities	(2,459)		(2,867)
Net change in cash, cash equivalents and restricted cash	722		108
Cash, cash equivalents and restricted cash at beginning of period	238		13
Cash, cash equivalents and restricted cash at end of period	$	960	$	121

The accompanying notes are an integral part of these consolidated financial statements.

6

MPLX LP

Consolidated Statements of Equity and Series A Preferred Units (Unaudited)

	Partnership
(In millions)	Common Unit-holders Public		Common Unit-holder MPC		Series B Preferred Unit-holders		Accumulated Other Comprehensive Loss		Non-controlling Interests		Total		Series A Preferred Unit-holders
Balance at December 31, 2022	$	8,413	$	3,293	$	611	$	(8)	$	237	$	12,546	$	968
Net income	323		592		5		—		9		929		23
Redemption of Series B preferred units	(2)		(3)		(595)		—		—		(600)		—
Distributions	(275)		(502)		(21)		—		(10)		(808)		(23)
Contributions	—		8		—		—		—		8		—
Other	—		—		—		4		1		5		—
Balance at March 31, 2023	$	8,459	$	3,388	$	—	$	(4)	$	237	$	12,080	$	968
Net income	322		588		—		—		9		919		23
Distributions	(274)		(502)		—		—		(9)		(785)		(23)
Contributions	—		5		—		—		—		5		—
Other	1		1		—		—		—		2		—
Balance at June 30, 2023	$	8,508	$	3,480	$	—	$	(4)	$	237	$	12,221	$	968
Net income	297		596		—		—		10		903		25
Unit repurchases	—		—		—		—		—		—		—
Distributions	(274)		(502)		—		—		(11)		(787)		(23)
Contributions	—		7		—		—		—		7		—
Other	2		—		—		—		—		2		—
Balance at September 30, 2023	$	8,533	$	3,581	$	—	$	(4)	$	236	$	12,346	$	970
	Partnership
	Common Unit-holders Public		Common Unit-holder MPC		Series B Preferred Unit-holders		Accumulated Other Comprehensive Loss		Non-controlling Interests		Total		Series A Preferred Unit-holders
Balance at December 31, 2021	$	8,579	$	2,638	$	611	$	(17)	$	241	$	12,052	$	965
Net income	287		506		11		—		8		812		21
Unit repurchases	(100)		—		—		—		—		(100)		—
Distributions	(260)		(456)		(21)		—		(9)		(746)		(21)
Contributions	—		10		—		—		—		10		—
Other	(1)		—		—		9		—		8		—
Balance at March 31, 2022	$	8,505	$	2,698	$	601	$	(8)	$	240	$	12,036	$	965
Net income	304		540		10		—		9		863		21
Unit repurchases	(35)		—		—		—		—		(35)		—
Distributions	(257)		(457)		—		—		(10)		(724)		(21)
Contributions	—		2		—		—		—		2		—
Other	1		1		—		—		—		2		—
Balance at June 30, 2022	$	8,518	$	2,784	$	611	$	(8)	$	239	$	12,144	$	965
Net income	502		893		10		—		9		1,414		23
Unit repurchases	(196)		—		—		—		—		(196)		—
Distributions	(258)		(456)		(20)		—		(10)		(744)		(21)
Contributions	—		55		—		—		—		55		—
Other	3		—		—		—		—		3		—
Balance at September 30, 2022	$	8,569	$	3,276	$	601	$	(8)	$	238	$	12,676	$	967

The accompanying notes are an integral part of these consolidated financial statements.

7

Notes to Consolidated Financial Statements (Unaudited)

1. Description of the Business and Basis of Presentation

Description of the Business

MPLX LP is a diversified, large-cap master limited partnership formed by Marathon Petroleum Corporation that owns and operates midstream energy infrastructure and logistics assets, and provides fuels distribution services. We are engaged in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products and renewables; the gathering, processing and transportation of natural gas; and the transportation, fractionation, storage and marketing of NGLs. MPLX’s principal executive office is located in Findlay, Ohio. MPLX was formed on March 27, 2012 as a Delaware limited partnership and completed its initial public offering on October 31, 2012.

MPLX’s business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”), which relates primarily to crude oil, refined products, other hydrocarbon-based products and renewables; and Gathering and Processing (“G&P”), which relates primarily to natural gas and NGLs. See Note 7 for additional information regarding the operations and results of these segments.

Basis of Presentation

These interim consolidated financial statements are unaudited; however, in the opinion of MPLX’s management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules and regulations of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by GAAP for complete financial statements. Certain information derived from our audited annual financial statements, prepared in accordance with GAAP, has been condensed or omitted from these interim financial statements.

These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2022. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the full year.

MPLX’s consolidated financial statements include all majority-owned and controlled subsidiaries. For non-wholly owned consolidated subsidiaries, the interests owned by third parties have been recorded as Noncontrolling interests on the accompanying Consolidated Balance Sheets. Intercompany accounts and transactions have been eliminated. MPLX’s investments in which MPLX exercises significant influence but does not control and does not have a controlling financial interest are accounted for using the equity method. MPLX’s investments in VIEs in which MPLX exercises significant influence but does not control and is not the primary beneficiary are also accounted for using the equity method.

2. Accounting Standards

Not Yet Adopted

ASU 2023-01, Leases (Topic 842): Common Control Arrangements

In March 2023, the FASB issued an ASU to amend certain provisions of ASC 842 that apply to arrangements between related parties under common control. The ASU amends the accounting for the amortization period of leasehold improvements in common-control leases for all entities and requires certain disclosures when the lease term is shorter than the useful life of the asset. This ASU is effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted. We do not expect the application of this ASU to have a material impact on our consolidated financial statements or financial disclosures.

8

3. Investments and Noncontrolling Interests

The following table presents MPLX’s equity method investments at the dates indicated:

		Ownership as of	Carrying value at
		September 30,	September 30,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	174	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	238		236
LOOP LLC		41%	301		287
MarEn Bakken Company LLC(1)		25%	453		475
Minnesota Pipe Line Company, LLC		17%	174		178
Whistler Pipeline LLC		38%	212		211
Other(2)	X		298		269
Total L&S			1,850		1,833
G&P
Centrahoma Processing LLC		40%	117		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	339		335
MarkWest Torñado GP, L.L.C.	X	60%	310		306
MarkWest Utica EMG, L.L.C.	X	58%	684		669
Rendezvous Gas Services, L.L.C.	X	78%	130		137
Sherwood Midstream Holdings LLC	X	51%	116		125
Sherwood Midstream LLC	X	50%	507		512
Other(2)	X		46		47
Total G&P			2,249		2,262
Total			$	4,099	$	4,095

(1)    The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL.    

(2)    Some investments included within Other have also been deemed to be VIEs.

For those entities that have been deemed to be VIEs, neither MPLX nor any of its subsidiaries have been deemed to be the primary beneficiary due to voting rights on significant matters. While we have the ability to exercise influence through participation in the management committees which make all significant decisions, we have equal influence over each committee as a joint interest partner and all significant decisions require the consent of the other investors without regard to economic interest. As such, we have determined that these entities should not be consolidated and applied the equity method of accounting with respect to our investments in each entity.

MPLX’s maximum exposure to loss as a result of its involvement with equity method investments includes its equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of its compensation received for the performance of the operating services. MPLX did not provide any financial support to equity method investments that it was not contractually obligated to provide during the nine months ended September 30, 2023. See Note 15 for information on our Guarantees related to indebtedness of equity method investees.

4. Related Party Agreements and Transactions

MPLX engages in transactions with both MPC and certain of its equity method investments as part of its normal business; however, transactions with MPC make up the majority of MPLX’s related party transactions. Transactions with related parties are further described below.

MPLX has various long-term, fee-based commercial agreements with MPC. Under these agreements, MPLX provides transportation, gathering, terminal, fuels distribution, marketing, storage, management, operational and other services to MPC. MPC has committed to provide MPLX with minimum quarterly throughput volumes on crude oil and refined products and other fees for storage capacity; operating and management fees; and reimbursements for certain direct and indirect costs. MPC has also committed to provide a fixed fee for 100 percent of available capacity for boats, barges and third-party chartered equipment under the marine transportation service agreement. MPLX also has a keep-whole commodity agreement with MPC under which MPC pays us a processing fee for NGLs related to keep-whole agreements and delivers shrink gas to the producers on our

9

behalf. We pay MPC a marketing fee in exchange for assuming the commodity risk. Additionally, MPLX has obligations to MPC for services provided to MPLX by MPC under omnibus and employee services-type agreements as well as other agreements.

During the second quarter of 2023, several terminal and storage services agreements with MPC were amended for certain items, including exercise of a five-year renewal option, with terms now extending to 2028.

Related Party Loan

MPLX is party to a loan agreement (the “MPC Loan Agreement”) with MPC. Under the terms of the MPC Loan Agreement, MPC extends loans to MPLX on a revolving basis as requested by MPLX and as agreed to by MPC. The borrowing capacity of the MPC Loan Agreement is $1.5 billion aggregate principal amount of all loans outstanding at any one time. The MPC Loan Agreement is scheduled to expire, and borrowings under the loan agreement are scheduled to mature and become due and payable, on July 31, 2024, provided that MPC may demand payment of all or any portion of the outstanding principal amount of the loan, together with all accrued and unpaid interest and other amounts (if any), at any time prior to maturity. Borrowings under the MPC Loan Agreement bear interest at one-month term SOFR adjusted upward by 0.10 percent plus 1.25 percent or such lower rate as would be applicable to such loans under the MPLX Credit Agreement as discussed in Note 11.

There was no activity on the MPC Loan Agreement for the nine months ended September 30, 2023.

Related Party Revenue

Related party sales to MPC primarily consist of crude oil and refined products pipeline based on tariff or contracted rates; storage, terminal and fuels distribution services based on contracted rates; and marine transportation services. Related party sales to MPC also consist of revenue related to volume deficiency credits.

MPLX also has operating agreements with MPC under which it receives a fee for operating MPC’s retained pipeline assets and a fixed annual fee for providing oversight and management services required to run the marine business. MPLX also receives management fee revenue for engineering, construction and administrative services for operating certain of its equity method investments. Amounts earned under these agreements are classified as Other income - related parties in the Consolidated Statements of Income.

Certain product sales to MPC and other related parties net to zero within the consolidated financial statements as the transactions are recorded net due to the terms of the agreements under which such product was sold. For the three and nine months ended September 30, 2023, these sales totaled $192 million and $540 million, respectively. For the three and nine months ended September 30, 2022, these sales totaled $235 million and $809 million, respectively.

Related Party Expenses

MPC charges MPLX for executive management services and certain general and administrative services provided to MPLX under the terms of our omnibus agreements (“Omnibus charges”) and for certain employee services provided to MPLX under employee services agreements (“ESA charges”). Omnibus charges and ESA charges are classified as Rental cost of sales - related parties, Purchases - related parties, or General and administrative expenses depending on the nature of the asset or activity with which the costs are associated. In addition to these agreements, MPLX purchases products from MPC, makes payments to MPC in its capacity as general contractor to MPLX, and has certain rent and lease agreements with MPC.

For the three and nine months ended September 30, 2023, General and administrative expenses incurred from MPC totaled $72 million and $197 million, respectively. For the three and nine months ended September 30, 2022, General and administrative expenses incurred from MPC totaled $60 million and $173 million, respectively.

Some charges incurred under the omnibus and employee service agreements are related to engineering services and are associated with assets under construction. These charges are added to Property, plant and equipment, net on the Consolidated Balance Sheets. For the three and nine months ended September 30, 2023, these charges totaled $28 million and $56 million, respectively. For the three and nine months ended September 30, 2022, these charges totaled $16 million and $54 million, respectively.

Related Party Assets and Liabilities

Assets and liabilities with related parties appearing in the Consolidated Balance Sheets are detailed in the table below. This table identifies the various components of related party assets and liabilities, including those associated with leases and deferred revenue on minimum volume commitments. If MPC fails to meet its minimum committed volumes, MPC will pay MPLX a deficiency payment based on the terms of the agreement. The deficiency amounts received under these agreements (excluding payments received under agreements classified as sales-type leases) are recorded as Current liabilities - related parties. In many cases, MPC may then apply the amount of any such deficiency payments as a credit for volumes in excess of its minimum volume commitment in future periods under the terms of the applicable agreements. MPLX recognizes related party revenues for the deficiency payments when credits are used for volumes in excess of minimum quarterly volume commitments, where it is

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probable the customer will not use the credit in future periods or upon the expiration of the credits. The use or expiration of the credits is a decrease in Current liabilities - related parties. Deficiency payments under agreements that have been classified as sales-type leases are recorded as a reduction against the corresponding lease receivable. In addition, capital projects MPLX undertakes at the request of MPC are reimbursed in cash and recognized as revenue over the remaining term of the applicable agreements or in some cases, as a contribution from MPC.

(In millions)	September 30, 2023		December 31, 2022
Current assets - related parties
Receivables	$	599	$	610
Lease receivables	140		111
Prepaid	14		5
Other	6		3
Total	759		729
Noncurrent assets - related parties
Long-term lease receivables	811		883
Right of use assets	227		228
Unguaranteed residual asset	115		87
Long-term receivables	21		27
Total	1,174		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	312		262
Deferred revenue	74		80
Operating lease liabilities	1		1
Total	387		343
Long-term liabilities - related parties
Long-term operating lease liabilities	226		228
Long-term deferred revenue	117		110
Total	$	343	$	338

(1)    There were no borrowings outstanding on the MPC Loan Agreement as of September 30, 2023 or December 31, 2022.

Other Related Party Transactions

From time to time, MPLX may also sell to or purchase from related parties, assets and inventory at the lesser of average unit cost or net realizable value.

5. Equity

The changes in the number of common units during the nine months ended September 30, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	196,428
Balance at September 30, 2023	1,001,217,044

Unit Repurchase Program

On August 2, 2022, we announced the board authorization for the repurchase of up to $1 billion of MPLX common units held by the public. This unit repurchase authorization has no expiration date. We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated unit repurchases, tender offers or open market solicitations for units, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time.

No units were repurchased during the three or nine months ended September 30, 2023. As of September 30, 2023, we had $846 million remaining under the unit repurchase authorization.

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Redemption of the Series B Preferred Units

On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series B preferred units”). MPLX paid unitholders the Series B preferred unit redemption price of $1,000 per unit.

Distributions on the Series B preferred units were payable semi-annually in arrears on the 15th day, or the first business day thereafter, of February and August of each year up to and including February 15, 2023. In accordance with these terms, MPLX made a final cash distribution of $21 million to Series B preferred unitholders on February 15, 2023, in conjunction with the redemption.

The changes in the Series B preferred unit balance during the nine months ended September 30, 2023 and September 30, 2022 are included in the Consolidated Statements of Equity within Series B preferred units.

Distributions

On October 24, 2023, MPLX declared a cash distribution for the third quarter of 2023, totaling $851 million, or $0.850 per common unit. This distribution will be paid on November 13, 2023 to common unitholders of record on November 3, 2023. This rate will also be received by Series A preferred unitholders.

Quarterly distributions for 2023 and 2022 are summarized below:

(Per common unit)	2023		2022
March 31,	$	0.775	$	0.705
June 30,	0.775		0.705
September 30,	$	0.850	$	0.775

The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three and nine months ended September 30, 2023 and September 30, 2022. Distributions, although earned, are not accrued until declared. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	851	$	777	$	2,403	$	2,204
Series A preferred unit distributions	25		23		71		65
Series B preferred unit distributions(1)	—		10		5		31
Total cash distributions declared	$	876	$	810	$	2,479	$	2,300

(1)    The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

6. Net Income Per Limited Partner Unit

Net income per unit applicable to common units is computed by dividing net income attributable to MPLX LP less income allocated to participating securities by the weighted average number of common units outstanding.

During the three and nine months ended September 30, 2023 and September 30, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units, and Series B preferred units and also had dilutive potential common units consisting of certain equity-based compensation awards. Potential common units omitted from the diluted earnings per unit calculation for the three and nine months ended September 30, 2023 and September 30, 2022 were less than 1 million.

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	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Net income attributable to MPLX LP	$	918	$	1,428	$	2,794	$	3,128
Less: Distributions declared on Series A preferred units	25		23		71		65
Distributions declared on Series B preferred units	—		10		5		31
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	851		777		2,403		2,204
Undistributed net gain attributable to MPLX LP	$	42	$	618	$	315	$	828

	Three Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	851	$	25	$	876
Undistributed net gain attributable to MPLX LP	41		1		42
Net income attributable to MPLX LP(1)	$	892	$	26	$	918
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.89
Diluted	$	0.89

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Three Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	777	$	23	$	10	$	810
Undistributed net gain attributable to MPLX LP(1)	600		18		—		618
Net income attributable to MPLX LP(2)	$	1,377	$	41	$	10	$	1,428
Weighted average units outstanding:
Basic	1,010
Diluted	1,011
Net income attributable to MPLX LP per limited partner unit:
Basic	$	1.36
Diluted	$	1.36

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the three months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

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	Nine Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,403	$	71	$	5	$	2,479
Undistributed net gain attributable to MPLX LP	306		9		—		315
Net income attributable to MPLX LP(1)	2,709		$	80	$	5	2,794
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	2,704					$	2,789
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.70
Diluted	$	2.70

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Nine Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,204	$	65	$	31	$	2,300
Undistributed net gain attributable to MPLX LP(1)	804		24		—		828
Net income attributable to MPLX LP(2)	$	3,008	$	89	$	31	$	3,128
Weighted average units outstanding:
Basic	1,012
Diluted	1,013
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.97
Diluted	$	2.97

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the nine months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

7. Segment Information

MPLX’s chief operating decision maker (“CODM”) is the chief executive officer of its general partner. The CODM reviews MPLX’s discrete financial information, makes operating decisions, assesses financial performance and allocates resources on a type of service basis. MPLX has two reportable segments: L&S and G&P. Each of these segments is organized and managed based upon the nature of the products and services it offers.

•L&S – gathers, transports, stores and distributes crude oil, refined products, other hydrocarbon-based products and renewables. Also includes the operation of refining logistics, fuels distribution and inland marine businesses, terminals, rail facilities, and storage caverns.

•G&P – gathers, processes and transports natural gas; and transports, fractionates, stores and markets NGLs.

Our CODM evaluates the performance of our segments using Segment Adjusted EBITDA. Amounts included in net income and excluded from Segment Adjusted EBITDA include: (i) depreciation and amortization; (ii) interest and other financial costs; (iii) income/(loss) from equity method investments; (iv) distributions and adjustments related to equity method investments; (v) gain on sales-type leases; (vi) impairment expense; (vii) noncontrolling interests; and (viii) other adjustments, as applicable. These items are either: (i) believed to be non-recurring in nature; (ii) not believed to be allocable or controlled by the segment; or (iii) are

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not tied to the operational performance of the segment. Assets by segment are not a measure used to assess the performance of the Partnership by our CODM and thus are not reported in our disclosures.

The tables below present information about revenues and other income, Segment Adjusted EBITDA, capital expenditures and investments in unconsolidated affiliates for our reportable segments:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
L&S
Service revenue	$	1,130	$	1,038	$	3,223	$	3,031
Rental income	216		210		638		593
Product related revenue	6		4		14		15
Sales-type lease revenue	129		118		379		343
Income from equity method investments	95		72		248		183
Other income	15		8		47		42
Total segment revenues and other income(1)	1,591		1,450		4,549		4,207
Segment Adjusted EBITDA(2)	1,091		969		3,139		2,839
Capital expenditures	73		80		251		238
Investments in unconsolidated affiliates	7		12		23		90
G&P
Service revenue	549		537		1,620		1,528
Rental income	52		66		155		239
Product related revenue	598		742		1,629		2,263
Sales-type lease revenue	34		28		101		28
Income from equity method investments	64		53		190		152
Other income(3)	24		525		71		534
Total segment revenues and other income(1)	1,321		1,951		3,766		4,744
Segment Adjusted EBITDA(2)	505		502		1,507		1,482
Capital expenditures	151		146		417		336
Investments in unconsolidated affiliates	$	6	$	30	$	67	$	108

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $564 million for the three and nine months ended September 30, 2023, respectively, and $175 million and $468 million for the three and nine months ended September 30, 2022, respectively. Third party revenues for the G&P segment were $1,248 million and $3,553 million for the three and nine months ended September 30, 2023, respectively, and $1,885 million and $4,551 million for the three and nine months ended September 30, 2022, respectively.

(2)    See below for the reconciliation from Segment Adjusted EBITDA to Net income.

(3)    The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

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The table below provides a reconciliation of Segment Adjusted EBITDA for reportable segments to Net income.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,091	$	969	$	3,139	$	2,839
G&P Segment Adjusted EBITDA	505		502		1,507		1,482
Total reportable segments	1,596		1,471		4,646		4,321
Depreciation and amortization(1)	(301)		(302)		(907)		(925)
Gain on sales-type leases	—		509		—		509
Interest and other financial costs	(225)		(236)		(701)		(691)
Income from equity method investments	159		125		438		335
Distributions/adjustments related to equity method investments	(208)		(166)		(551)		(450)
Adjusted EBITDA attributable to noncontrolling interests	11		10		31		29
Garyville incident response costs(2)	(63)		—		(63)		—
Other(3)	(41)		26		(71)		26
Net income	$	928	$	1,437	$	2,822	$	3,154

(1)    Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

(2)    In August 2023, a naphtha release and resulting fire occurred at our Garyville Tank Farm resulting in the loss of four storage tanks with a combined shell capacity of 894 thousand barrels. We incurred $63 million of incident response costs during the three and nine months ended September 30, 2023.

(3)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

8. Property, Plant and Equipment

Property, plant and equipment with associated accumulated depreciation is shown below:

	September 30, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,633	$	3,919	$	8,714	$	12,416	$	3,554	$	8,862
G&P	13,844		3,938		9,906		13,495		3,509		9,986
Total	$	26,477	$	7,857	$	18,620	$	25,911	$	7,063	$	18,848

We capitalize interest as part of the cost of major projects during the construction period. Capitalized interest totaled $4 million and $11 million for the three and nine months ended September 30, 2023, respectively, and $2 million and $7 million for the three and nine months ended September 30, 2022, respectively.

9. Fair Value Measurements

Fair Values – Recurring

The following table presents the impact on the Consolidated Balance Sheets of MPLX’s financial instruments carried at fair value on a recurring basis as of September 30, 2023 and December 31, 2022 by fair value hierarchy level.

	September 30, 2023				December 31, 2022
(In millions)	Asset		Liability		Asset		Liability
Commodity contracts (Level 2)
Other current assets / Other current liabilities	$	2	$	—	$	—	$	—
Embedded derivatives in commodity contracts (Level 3)
Other current assets / Other current liabilities	—		10		—		10
Other noncurrent assets / Other long-term liabilities	—		50		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	60	$	—	$	61

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Level 2 instruments include over-the-counter fixed swaps to mitigate the price risk from our sales of propane. The swap valuations are based on observable inputs in the form of forward prices based on Mont Belvieu propane forward spot prices and contain no significant unobservable inputs.

Level 3 instruments relate to an embedded derivative liability for a natural gas purchase commitment embedded in a keep-whole processing agreement. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.61 to $1.66 per gallon with a weighted average of $0.79 per gallon and (2) a 100 percent probability of renewal for the five-year renewal term of the gas purchase commitment and related keep-whole processing agreement. Increases or decreases in the fractionation spread result in an increase or decrease in the fair value of the embedded derivative liability, respectively.

Changes in Level 3 Fair Value Measurements

The following table is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Beginning balance	$	(53)	$	(92)	$	(61)	$	(108)
Unrealized and realized (loss)/gain included in Net Income(1)	(10)		44		(7)		52
Settlements	3		2		8		10
Ending balance	$	(60)	$	(46)	$	(60)	$	(46)
The amount of total (loss)/gain for the period included in earnings attributable to the change in unrealized gain relating to liabilities still held at end of period	$	(9)	$	42	$	(6)	$	50

(1)     (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.

Fair Values – Reported

We believe the carrying value of our other financial instruments, including cash and cash equivalents, receivables, receivables from related parties, lease receivables, lease receivables from related parties, accounts payable, and payables to related parties, approximate fair value. MPLX’s fair value assessment incorporates a variety of considerations, including the duration of the instruments, MPC’s investment-grade credit rating, and the historical incurrence of and expected future insignificance of bad debt expense, which includes an evaluation of counterparty credit risk. The recorded value of the amounts outstanding under the bank revolving credit facility, if any, approximates fair value due to the variable interest rate that approximates current market rates. Derivative instruments are recorded at fair value, based on available market information (see Note 10).

The fair value of MPLX’s debt is estimated based on prices from recent trade activity and is categorized in Level 3 of the fair value hierarchy. The following table summarizes the fair value and carrying value of our third-party debt, excluding finance leases and unamortized debt issuance costs:

	September 30, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	17,922	$	20,536	$	18,095	$	19,905

(1)    Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

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10. Derivatives

As of September 30, 2023, MPLX had the following outstanding commodity contracts that were executed to manage the price risk associated with sales of propane during 2023:

Derivative contracts not designated as hedging instruments	Financial Position	Notional Quantity
Propane (gallons)	Short	16,827,000

Embedded Derivative - MPLX has a natural gas purchase commitment embedded in a keep-whole processing agreement with a producer customer in the Southern Appalachian region expiring in December 2027. The customer has the unilateral option to extend the agreement for one five-year term through December 2032. For accounting purposes, the natural gas purchase commitment and the term extending option have been aggregated into a single compound embedded derivative. The probability of the customer exercising its option is determined based on assumptions about the customer’s potential business strategy decision points that may exist at the time they would elect whether to renew the contract. The changes in fair value of this compound embedded derivative are based on the difference between the contractual and index pricing, the probability of the producer customer exercising its option to extend, and the estimated favorability of these contracts compared to current market conditions. The changes in fair value are recorded in earnings through Purchased product costs in the Consolidated Statements of Income. For further information regarding the fair value measurement of derivative instruments, see Note 9. As of September 30, 2023 and December 31, 2022, the estimated fair value of this contract was a liability of $60 million and $61 million, respectively.

Certain derivative positions are subject to master netting agreements; therefore, MPLX has elected to offset derivative assets and liabilities that are legally permissible to be offset. As of September 30, 2023 and December 31, 2022, there were no derivative assets or liabilities that were offset in the Consolidated Balance Sheets.

We make a distinction between realized or unrealized gains and losses on derivatives. During the period when a derivative contract is outstanding, changes in the fair value of the derivative are recorded as an unrealized gain or loss. When a derivative contract matures or is settled, the previously recorded unrealized gain or loss is reversed, and the realized gain or loss of the contract is recorded. The impact of MPLX’s derivative contracts not designated as hedging instruments and the location of gains and losses recognized in the Consolidated Statements of Income is summarized below:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Product sales:
Realized gain	$	3	$	—	$	3	$	—
Unrealized (loss)/gain	(8)		—		2		—
Product sales derivative (loss)/gain	(5)		—		5		—
Purchased product costs:
Realized loss	(3)		(2)		(8)		(10)
Unrealized (loss)/gain	(7)		46		1		62
Purchased produce cost derivative (loss)/gain	(10)		44		(7)		52
Total derivative (loss)/gain included in Net income	$	(15)	$	44	$	(2)	$	52

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11. Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	September 30, 2023		December 31, 2022
MPLX LP:
MPLX Credit Agreement	$	—	$	—
Fixed rate senior notes	20,657		20,046
Consolidated subsidiaries:
MarkWest	12		23
ANDX	31		31
Finance lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(125)		(117)
Unamortized discount	(164)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,417	$	18,808

Credit Agreement

MPLX’s credit agreement (the “MPLX Credit Agreement”) matures in July 2027 and, among other things, provides for a $2 billion unsecured revolving credit facility and letter of credit issuing capacity under the facility of up to $150 million. Letter of credit issuing capacity is included in, not in addition to, the $2 billion borrowing capacity. Borrowings under the MPLX Credit Agreement bear interest, at MPLX’s election, at either the Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin.

There was no activity on the MPLX Credit Agreement during the nine months ended September 30, 2023.

Fixed Rate Senior Notes

MPLX’s senior notes, including those issued by consolidated subsidiaries, consist of various series of senior notes maturing between 2024 and 2058 with interest rates ranging from 1.750 percent to 5.650 percent. Interest on each series of notes is payable semi-annually in arrears on various dates depending on the series of the notes.

On February 9, 2023, MPLX issued $1.6 billion aggregate principal amount of notes, consisting of $1.1 billion principal amount of 5.00 percent senior notes due 2033 (the “2033 Senior Notes”) and $500 million principal amount of 5.65 percent senior notes due 2053 (the “2053 Senior Notes”). The 2033 Senior Notes were offered at a price to the public of 99.170 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023. The 2053 Senior Notes were offered at a price to the public of 99.536 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023.

On February 15, 2023, MPLX used $600 million of the net proceeds from the offering of the 2033 Senior Notes and 2053 Senior Notes described above to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the offering, and cash on hand, to redeem all of MPLX’s and MarkWest’s $1.0 billion aggregate principal amount of 4.50 percent senior notes due July 2023, at par, plus accrued and unpaid interest. The redemption resulted in a loss of $9 million due to the immediate expense recognition of unamortized debt discount and issuance costs for the three months ended March 31, 2023, which is included on the Consolidated Statements of Income as Other financial costs, net.

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12. Revenue

Disaggregation of Revenue

The following tables represent a disaggregation of revenue for each reportable segment for the three and nine months ended September 30, 2023 and September 30, 2022:

	Three Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	97	$	544	$	641
Service revenue - related parties	1,033		5		1,038
Service revenue - product related	—		75		75
Product sales	2		476		478
Product sales - related parties	4		47		51
Total revenues from contracts with customers	$	1,136	$	1,147	2,283
Non-ASC 606 revenue(1)					629
Total revenues and other income					$	2,912

	Three Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	94	$	533	$	627
Service revenue - related parties	944		4		948
Service revenue - product related	—		83		83
Product sales	2		615		617
Product sales - related parties	2		44		46
Total revenues from contracts with customers	$	1,042	$	1,279	2,321
Non-ASC 606 revenue(1)					1,080
Total revenues and other income					$	3,401

	Nine Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	272	$	1,609	$	1,881
Service revenue - related parties	2,951		11		2,962
Service revenue - product related	—		214		214
Product sales	4		1,270		1,274
Product sales - related parties	10		145		155
Total revenues from contracts with customers	$	3,237	$	3,249	6,486
Non-ASC 606 revenue(1)					1,829
Total revenues and other income					$	8,315

	Nine Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	243	$	1,515	$	1,758
Service revenue - related parties	2,788		13		2,801
Service revenue - product related	—		324		324
Product sales	5		1,807		1,812
Product sales - related parties	10		132		142
Total revenues from contracts with customers	$	3,046	$	3,791	6,837
Non-ASC 606 revenue(1)					2,114
Total revenues and other income					$	8,951

(1)    Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.

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Contract Balances

Our receivables are primarily associated with customer contracts. Payment terms vary by product or service type; however, the period between invoicing and payment is not significant. Included within the receivables are balances related to commodity sales on behalf of our producer customers, for which we remit the net sales price back to the producer customers upon completion of the sale. These balances are included in Receivables, net on the Consolidated Balance Sheets.

Under certain of our contracts, we recognize revenues in excess of billings which we present as contract assets. Contract assets typically relate to deficiency payments related to minimum volume commitments and aid in construction agreements where the revenue recognized and MPLX’s rights to consideration for work completed exceeds the amount billed to the customer. Contract assets are included in Other current assets and Other noncurrent assets on the Consolidated Balance Sheets.

Under certain of our contracts, we receive payments in advance of satisfying our performance obligations, which are recorded as contract liabilities. Contract liabilities, which we present as Deferred revenue and Long-term deferred revenue, typically relate to advance payments for aid in construction agreements and deferred customer credits associated with makeup rights and minimum volume commitments. Related to minimum volume commitments, breakage is estimated and recognized into service revenue in instances where it is probable the customer will not use the credit in future periods. We classify contract liabilities as current or long-term based on the timing of when we expect to recognize revenue.

The tables below reflect the changes in ASC 606 contract balances for the nine-month periods ended September 30, 2023 and September 30, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2023
Contract assets	$	21	$	(19)	$	—	$	2
Long-term contract assets	1		—		—		1
Deferred revenue	57		24		(31)		50
Deferred revenue - related parties	63		63		(72)		54
Long-term deferred revenue	216		76		—		292
Long-term deferred revenue - related parties	25		5		—		30
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2022
Contract assets	$	25	$	(9)	$	—	$	16
Long-term contract assets	2		—		—		2
Deferred revenue	56		40		(33)		63
Deferred revenue - related parties	60		79		(83)		56
Long-term deferred revenue	135		27		—		162
Long-term deferred revenue - related parties	31		(5)		—		26
Long-term contract liabilities	$	5	$	(1)	$	—	$	4

(1)     No significant revenue was recognized related to past performance obligations in the current periods.

Remaining Performance Obligations

The table below includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) as of September 30, 2023. The amounts presented below are generally limited to fixed consideration from contracts with customers that contain minimum volume commitments.

A significant portion of our future contracted revenue is excluded from the amounts presented below in accordance with ASC 606. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded from this disclosure. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less, or that are terminable by our customer with little or no termination penalties. Potential future performance obligations related to renewals that have not yet been exercised or are not certain of exercise are

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excluded from the amounts presented below. Revenues classified as Rental income and Sales-type lease revenue are also excluded from this table.

(In billions)
2023	$	0.5
2024	2.0
2025	1.9
2026	1.7
2027	1.6
Thereafter	1.0
Total estimated revenue on remaining performance obligations	$	8.7

As of September 30, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $426 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 20 years. A portion of this amount is not disclosed in the table above as it is deemed variable consideration due to volume variability.

13. Supplemental Cash Flow Information

	Nine Months Ended  September 30,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	724	$	642
Income taxes paid	4		2
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	8		—
Net transfers of property, plant and equipment to lease receivable	$	86	$	20

The Consolidated Statements of Cash Flows exclude changes to the Consolidated Balance Sheets that do not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures:

	Nine Months Ended  September 30,
(In millions)	2023		2022
Additions to property, plant and equipment	$	662	$	535
Increase in capital accruals	6		39
Total capital expenditures	$	668	$	574

14. Leases

During the third quarter of 2022, the approved expansion of a gathering and compression system triggered the first assessment of the related third-party agreement under ASC 842. Similarly, an amendment to extend the term of our butane storage service agreement with MPC triggered the first assessment of the related-party agreement under ASC 842. As a result of the assessments during the third quarter of 2022, the leases were reclassified from operating leases to sales-type leases. Accordingly, the underlying property, plant and equipment, net, and associated deferred revenue, if any, were derecognized. The present value of the future lease payments and the unguaranteed residual value of the assets were recorded as a net investment in sales-type lease during the period.

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The following presents the consolidated financial statement impact of the sales-type lease modifications discussed above. These transactions, including any related gains recognized in the Consolidated Statements of Income, were non-cash transactions.

	Three Months Ended  September 30, 2022
(In millions)	Related Party(1)		Third Party(2)
Lease receivables	$	79	$	914
Unguaranteed residual assets	6		63
Property, plant and equipment, net	(42)		(745)
Deferred revenue	—		277
Amount recognized on commencement date	$	43	$	509

(1)    The amount recognized on commencement date was recorded as a Contribution from MPC in the Consolidated Statements of Equity given the underlying agreements are between entities under common control.

(2)    The amount recognized on commencement date was recorded as a gain in Other income in the Consolidated Statements of Income.

15. Commitments and Contingencies

MPLX is the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which MPLX has not recorded a liability, MPLX is unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings, discovery or court proceedings. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material.

Environmental Matters

MPLX is subject to federal, state and local laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites. Penalties may be imposed for non-compliance.

Accrued liabilities for remediation totaled $23 million at September 30, 2023 and $17 million December 31, 2022. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties, if any, that may be imposed.

MPLX is involved in environmental enforcement matters arising in the ordinary course of business. While the outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on its consolidated results of operations, financial position or cash flows.

Other Legal Proceedings

In July 2020, Tesoro High Plains Pipeline Company, LLC (“THPP”), a subsidiary of MPLX, received a Notification of Trespass Determination from the Bureau of Indian Affairs (“BIA”) relating to a portion of the Tesoro High Plains Pipeline that crosses the Fort Berthold Reservation in North Dakota. The notification demanded the immediate cessation of pipeline operations and assessed trespass damages of approximately $187 million. After subsequent appeal proceedings and in compliance with a new order issued by the BIA, in December 2020, THPP paid approximately $4 million in assessed trespass damages and ceased use of the portion of the pipeline that crosses the property at issue. In March 2021, the BIA issued an order purporting to vacate the BIA's prior orders related to THPP’s alleged trespass and direct the Regional Director of the BIA to reconsider the issue of THPP’s alleged trespass and issue a new order. In April 2021, THPP filed a lawsuit in the District of North Dakota against the United States of America, the U.S. Department of the Interior and the BIA (together, the “U.S. Government Parties”) challenging the March 2021 order purporting to vacate all previous orders related to THPP’s alleged trespass. On February 8, 2022, the U.S. Government Parties filed their answer and counterclaims to THPP’s suit claiming THPP is in continued trespass with respect to the pipeline and seeking disgorgement of pipeline profits from June 1, 2013 to present, removal of the pipeline and remediation. We intend to vigorously defend ourselves against these counterclaims.

MPLX is also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these other lawsuits and proceedings will not, individually or collectively, have a material adverse effect on its consolidated financial position, results of operations or cash flows.

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Guarantees related to indebtedness of equity method investees

We hold a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The Army Corps has not provided a definitive date as to when a final decision would be issued.

In May 2021, the D.D.C. denied a renewed request for an injunction to shut down the pipeline while the EIS is being prepared. In June 2021, the D.D.C. issued an order dismissing without prejudice the tribes’ claims against the Dakota Access Pipeline. The litigation could be reopened or new litigation challenging the EIS, once completed, could be filed. The pipeline remains operational.

We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system.

If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of September 30, 2023, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.

Contractual Commitments and Contingencies

From time to time and in the ordinary course of business, MPLX and its affiliates provide guarantees of MPLX’s subsidiaries payment and performance obligations in the G&P segment. Certain natural gas processing and gathering arrangements require MPLX to construct new natural gas processing plants, natural gas gathering pipelines and NGL pipelines and contain certain fees and charges if specified construction milestones are not achieved for reasons other than force majeure. In certain cases, certain producers may have the right to cancel the processing arrangements if there are significant delays that are not due to force majeure. As of September 30, 2023, management does not believe there are any indications that MPLX will not be able to meet the construction milestones, that force majeure does not apply or that such fees and charges will otherwise be triggered.

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Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Management’s Discussion and Analysis of Financial Condition and Results of Operations should also be read in conjunction with the unaudited consolidated financial statements and accompanying footnotes included under Item 1. Financial Statements and in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2022.

Disclosures Regarding Forward-Looking Statements

This Quarterly Report on Form 10-Q, particularly Management’s Discussion and Analysis of Financial Condition and Results of Operations and Quantitative and Qualitative Disclosures about Market Risk, includes forward-looking statements that are subject to risks, contingencies or uncertainties. You can identify forward-looking statements by words such as “anticipate,” “believe,” “commitment,” “could,” “design,” “estimate,” “expect,” “forecast,” “goal,” “guidance,” “intend,” “may,” “objective,” “opportunity,” “outlook,” “plan,” “policy,” “position,” “potential,” “predict,” “priority,” “project,” “prospective,” “pursue,” “seek,” “should,” “strategy,” “target,” “will,” “would” or other similar expressions that convey the uncertainty of future events or outcomes.

Forward-looking statements include, among other things, statements regarding:

•future financial and operating results;

•environmental, social and governance (“ESG”) plans and goals, including those related to greenhouse gas emissions, diversity and inclusion and ESG reporting;

•future levels of capital, environmental or maintenance expenditures, general and administrative and other expenses;

•the success or timing of completion of ongoing or anticipated capital or maintenance projects;

•business strategies, growth opportunities and expected investments;

•the timing and amount of future distributions or unit repurchases; and

•the anticipated effects of actions of third parties such as competitors, activist investors, federal, foreign, state or local regulatory authorities, or plaintiffs in litigation.

Our forward-looking statements are not guarantees of future performance and you should not rely unduly on them, as they involve risks, uncertainties and assumptions that we cannot predict. Forward-looking and other statements regarding our ESG plans and goals are not an indication that these statements are material to investors or required to be disclosed in our filings with the SEC. In addition, historical, current, and forward-looking ESG-related statements may be based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve, and assumptions that are subject to change in the future. Material differences between actual results and any future performance suggested in our forward-looking statements could result from a variety of factors, including the following:

•general economic, political or regulatory developments, including inflation, interest rates, changes in governmental policies relating to refined petroleum products, crude oil, natural gas, NGLs, renewables, or taxation;

•the ability of MPC to achieve its strategic objectives and the effects of those strategic decisions on us;

•further impairments;

•negative capital market conditions, including an increase of the current yield on common units;

•the ability to achieve strategic and financial objectives, including with respect to distribution coverage, future distribution levels, proposed projects and completed transactions;

•the success of MPC’s portfolio optimization, including the ability to complete any divestitures on commercially reasonable terms and/or within the expected timeframe, and the effects of any such divestitures on our business, financial condition, results of operations and cash flows;

•the adequacy of capital resources and liquidity, including the availability of sufficient cash flow to pay distributions and access to debt on commercially reasonable terms, and the ability to successfully execute business plans, growth strategies and self-funding models;

•the timing and extent of changes in commodity prices and demand for crude oil, refined products, feedstocks or other hydrocarbon-based products, or renewables;

•volatility in or degradation of general economic, market, industry or business conditions as a result of the COVID-19 pandemic, other infectious disease outbreaks, natural hazards, extreme weather events, hostilities in the Middle East, the military conflict between Russia and Ukraine, other conflicts, inflation, rising interest rates or otherwise;

•changes to the expected construction costs and timing of projects and planned investments, and the ability to obtain regulatory and other approvals with respect thereto;

•completion of midstream infrastructure by competitors;

•disruptions due to equipment interruption or failure, including electrical shortages and power grid failures;

•the suspension, reduction or termination of MPC’s obligations under MPLX’s commercial agreements;

•modifications to financial policies, capital budgets, and earnings and distributions;

•the ability to manage disruptions in credit markets or changes to credit ratings;

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•compliance with federal and state environmental, economic, health and safety, energy and other policies and regulations or enforcement actions initiated thereunder;

•adverse results in litigation;

•the effect of restructuring or reorganization of business components;

•the potential effects of changes in tariff rates on our business, financial condition, results of operations and cash flows;

•foreign imports and exports of crude oil, refined products, natural gas and NGLs;

•changes in producer customers’ drilling plans or in volumes of throughput of crude oil, natural gas, NGLs, refined products, other hydrocarbon-based products, or renewables;

•changes in the cost or availability of third-party vessels, pipelines, railcars and other means of transportation for crude oil, natural gas, NGLs, feedstocks, refined products, or renewables;

•the price, availability and acceptance of alternative fuels and alternative-fuel vehicles and laws mandating such fuels or vehicles;

•actions taken by our competitors, including pricing adjustments and the expansion and retirement of pipeline capacity, processing, fractionation and treating facilities in response to market conditions;

•expectations regarding joint venture arrangements and other acquisitions or divestitures of assets;

•midstream and refining industry overcapacity or undercapacity;

•accidents or other unscheduled shutdowns affecting our machinery, pipelines, processing, fractionation and treating facilities or equipment, means of transportation, or those of our suppliers or customers;

•our ability to maintain adequate insurance coverage and recover insurance proceeds to offset losses resulting from accidents or other insurance incidents and unscheduled shutdowns;

•acts of war, terrorism or civil unrest that could impair our ability to gather, process, fractionate or transport crude oil, natural gas, NGLs, refined products, or renewables;

•political pressure and influence of environmental groups upon policies and decisions related to the production, gathering, refining, processing, fractionation, transportation and marketing of crude oil or other feedstocks, refined products, natural gas, NGLs, other hydrocarbon-based products, or renewables;

•the imposition of windfall profit taxes or maximum refining margin penalties on companies operating in the energy industry in California or other jurisdictions; and

•our ability to successfully achieve our ESG goals and targets within the expected timeframe, if at all.

For additional risk factors affecting our business, see the risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2022. We undertake no obligation to update any forward-looking statements except to the extent required by applicable law.

MPLX Overview

We are a diversified, large-cap master limited partnership formed by MPC in 2012 that owns and operates midstream energy infrastructure and logistics assets, and provides fuels distribution services. The business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”) and Gathering and Processing (“G&P”). The L&S segment primarily engages in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products, and renewables. The L&S segment also includes the operation of our refining logistics, fuels distribution and inland marine businesses, terminals, rail facilities and storage caverns. The G&P segment provides gathering, processing and transportation of natural gas as well as the transportation, fractionation, storage and marketing of NGLs.

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Significant Financial and Other Highlights

Significant financial highlights for the three months ended September 30, 2023 and September 30, 2022 are shown in the chart below. Refer to the Results of Operations, the Liquidity and Capital Resources, and Non-GAAP Financial Information sections for further information.

(1)     The 2022 amounts include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

(2)    Non-GAAP measure. See reconciliations that follow for the most directly comparable GAAP measures.

Other Highlights

•Returned $799 million and $2,419 million of capital to unitholders in the three and nine months ended September 30, 2023, via distributions.

•Announced a third quarter 2023 distribution of $0.850 per common unit, representing a 10% increase over the prior quarter’s distribution.

Garyville Tank Farm Incident

In August 2023, a naphtha release and resulting fire occurred at our Garyville Tank Farm (“Garyville Incident”), resulting in the loss of four storage tanks with a combined shell capacity of 894 thousand barrels. We incurred $63 million of incident response costs during the three and nine months ended September 30, 2023. We are pursuing recovery of property damage and incident response costs under the relevant insurance policies, although there can be no assurance as to the amount of recovery, if any.

Current Economic Environment

In an effort to ease inflation in support of its monetary policy goals, the Federal Reserve has raised interest rates multiple times throughout 2022 and 2023. We cannot predict the effect of higher interest rates, the concern of a recession, or the impact of inflation and fuel prices on demand for our services. In response to this business environment, MPLX remains focused on executing its strategic priorities of strict capital discipline, fostering a low-cost culture, and portfolio optimization. Also, to the extent permitted by regulations and our existing agreements, many of which provide for inflation-based adjustments, we have increased the fees we charge our customers to reflect higher levels of inflation.

Succession Planning

As previously disclosed, MPC maintains a mandatory retirement policy that, absent a waiver or extension, requires an executive officer to retire from service to the company coincident with, or immediately following, the first of the month after such executive officer reaches age 65 (the "Policy"). Michael J. Hennigan, President and Chief Executive Officer of our general partner, as well as the President and Chief Executive Officer of MPC, will reach mandatory retirement on August 1, 2024. Accordingly, the MPC Board of Directors, with a focus on the long-term strategic direction of the company, is engaged in appropriate succession planning activities, which are expected to include, among other customary steps, the review of succession candidates, as well as consideration of any waiver or extension of the Policy respecting Mr. Hennigan.

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Non-GAAP Financial Information

Our management uses a variety of financial and operating metrics to analyze our performance. These metrics are significant factors in assessing our operating results and profitability and include the non-GAAP financial measures of Adjusted EBITDA, DCF, adjusted free cash flow (“Adjusted FCF”), and Adjusted FCF after distributions. The amount of Adjusted EBITDA and DCF generated is considered by the board of directors of our general partner in approving MPLX’s cash distributions.

We define Adjusted EBITDA as net income adjusted for: (i) provision for income taxes; (ii) interest and other financial costs; (iii) depreciation and amortization; (iv) income/(loss) from equity method investments; (v) distributions and adjustments related to equity method investments; (vi) gain on sales-type leases; (vii) impairment expense; (viii) noncontrolling interests; and (ix) other adjustments, as applicable. We also use DCF, which we define as Adjusted EBITDA adjusted for: (i) deferred revenue impacts; (ii) sales-type lease payments, net of income; (iii) net interest and other financial costs; (iv) net maintenance capital expenditures; (v) equity method investment capital expenditures paid out; and (vi) other adjustments as deemed necessary.

We define Adjusted FCF as net cash provided by operating activities adjusted for: (i) net cash used in investing activities; (ii) cash contributions from MPC; and (iii) cash distributions to noncontrolling interests. We define Adjusted FCF after distributions as Adjusted FCF less base distributions to common and preferred unitholders.

We believe that the presentation of Adjusted EBITDA, DCF, Adjusted FCF and Adjusted FCF after distributions provides useful information to investors in assessing our financial condition and results of operations. The GAAP measures most directly comparable to Adjusted EBITDA and DCF are net income and net cash provided by operating activities while the GAAP measure most directly comparable to Adjusted FCF and Adjusted FCF after distributions is net cash provided by operating activities. These non-GAAP financial measures should not be considered alternatives to GAAP net income or net cash provided by operating activities as they have important limitations as analytical tools because they exclude some but not all items that affect net income and net cash provided by operating activities or any other measure of financial performance or liquidity presented in accordance with GAAP. These non-GAAP financial measures should not be considered in isolation or as substitutes for analysis of our results as reported under GAAP. Additionally, because non-GAAP financial measures may be defined differently by other companies in our industry, our definitions may not be comparable to similarly titled measures of other companies, thereby diminishing their utility. For a reconciliation of Adjusted EBITDA and DCF to their most directly comparable measures calculated and presented in accordance with GAAP, see Results of Operations. For a reconciliation of Adjusted FCF and Adjusted FCF after distributions to their most directly comparable measure calculated and presented in accordance with GAAP, see Liquidity and Capital Resources.

Comparability of our Financial Results

During the normal course of business, we amend or modify our contractual agreements with customers. These amendments or modifications require the agreements to be reassessed under ASU No. 2016-02, Leases (“ASC 842”), which can impact the classification of revenues or costs associated with the agreement. These reassessments may impact the comparability of our financial results.

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Results of Operations

The following tables and discussion summarize our results of operations, including a reconciliation of Adjusted EBITDA and DCF from Net income and Net cash provided by operating activities, to the most directly comparable GAAP financial measures. This discussion should be read in conjunction with Item 1. Financial Statements and is intended to provide investors with a reasonable basis for assessing our historical operations, but should not serve as the only criteria for predicting our future performance.

	Three Months Ended September 30,						Nine Months Ended September 30,
(In millions)	2023		2022		Variance		2023		2022		Variance
Revenues and other income:
Total revenues and other income(1)	$	2,912	$	3,401	$	(489)	$	8,315	$	8,951	$	(636)
Costs and expenses:
Cost of revenues (excludes items below)	367		371		(4)		1,023		981		42
Purchased product costs	474		540		(66)		1,234		1,670		(436)
Rental cost of sales	20		22		(2)		60		101		(41)
Rental cost of sales - related parties	8		10		(2)		24		44		(20)
Purchases - related parties	442		364		78		1,160		1,034		126
Depreciation and amortization	301		302		(1)		907		925		(18)
General and administrative expenses	102		88		14		280		248		32
Other taxes	44		30		14		102		97		5
Total costs and expenses	1,758		1,727		31		4,790		5,100		(310)
Income from operations	1,154		1,674		(520)		3,525		3,851		(326)
Related-party interest and other financial costs	—		—		—		—		5		(5)
Interest expense, net of amounts capitalized	223		217		6		673		627		46
Other financial costs, net	2		19		(17)		28		59		(31)
Income before income taxes	929		1,438		(509)		2,824		3,160		(336)
Provision for income taxes	1		1		—		2		6		(4)
Net income	928		1,437		(509)		2,822		3,154		(332)
Less: Net income attributable to noncontrolling interests	10		9		1		28		26		2
Net income attributable to MPLX LP	918		1,428		(510)		2,794		3,128		(334)
Adjusted EBITDA attributable to MPLX LP(2)	1,596		1,471		125		4,646		4,321		325
DCF attributable to MPLX(2)	$	1,373	$	1,264	$	109	$	3,956	$	3,711	$	245

(1)     The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

(2)    Non-GAAP measure. See reconciliation below to the most directly comparable GAAP measures.

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	Three Months Ended September 30,						Nine Months Ended September 30,
(In millions)	2023		2022		Variance		2023		2022		Variance
Reconciliation of Adjusted EBITDA attributable to MPLX LP and DCF attributable to GP and LP unitholders from Net income:
Net income	$	928	$	1,437	$	(509)	$	2,822	$	3,154	$	(332)
Provision for income taxes	1		1		—		2		6		(4)
Interest and other financial costs	225		236		(11)		701		691		10
Income from operations	1,154		1,674		(520)		3,525		3,851		(326)
Depreciation and amortization	301		302		(1)		907		925		(18)
Income from equity method investments	(159)		(125)		(34)		(438)		(335)		(103)
Distributions/adjustments related to equity method investments	208		166		42		551		450		101
Gain on sales-type leases	—		(509)		509		—		(509)		509
Garyville Incident response costs	63		—		63		63		—		63
Other(1)	40		(27)		67		69		(32)		101
Adjusted EBITDA	1,607		1,481		126		4,677		4,350		327
Adjusted EBITDA attributable to noncontrolling interests	(11)		(10)		(1)		(31)		(29)		(2)
Adjusted EBITDA attributable to MPLX LP	1,596		1,471		125		4,646		4,321		325
Deferred revenue impacts	25		39		(14)		65		87		(22)
Sales-type lease payments, net of income	3		3		—		9		13		(4)
Net interest and other financial costs(2)	(212)		(216)		4		(650)		(635)		(15)
Maintenance capital expenditures, net of reimbursements	(28)		(40)		12		(93)		(93)		—
Equity method investment maintenance capital expenditures paid out	(4)		(4)		—		(11)		(10)		(1)
Other	(7)		11		(18)		(10)		28		(38)
DCF attributable to MPLX LP	1,373		1,264		109		3,956		3,711		245
Preferred unit distributions	(25)		(33)		8		(76)		(96)		20
DCF attributable to GP and LP unitholders	$	1,348	$	1,231	$	117	$	3,880	$	3,615	$	265

(1)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation and other miscellaneous items.

(2)    Excludes gain/loss on extinguishment of debt and amortization of deferred financing costs.

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	Three Months Ended September 30,						Nine Months Ended September 30,
(In millions)	2023		2022		Variance		2023		2022		Variance
Reconciliation of Adjusted EBITDA attributable to MPLX LP and DCF attributable to GP and LP unitholders from Net cash provided by operating activities:
Net cash provided by operating activities	$	1,244	$	1,039	$	205	$	3,908	$	3,651	$	257
Changes in working capital items	56		208		(152)		(56)		60		(116)
All other, net	(9)		(15)		6		(12)		(51)		39
Loss on extinguishment of debt	—		1		(1)		9		1		8
Net interest and other financial costs(1)	212		216		(4)		650		635		15
Other adjustments to equity method investment distributions	13		19		(6)		25		45		(20)
Garyville Incident response costs	63		—		63		63		—		63
Other	28		13		15		90		9		81
Adjusted EBITDA	1,607		1,481		126		4,677		4,350		327
Adjusted EBITDA attributable to noncontrolling interests	(11)		(10)		(1)		(31)		(29)		(2)
Adjusted EBITDA attributable to MPLX LP	1,596		1,471		125		4,646		4,321		325
Deferred revenue impacts	25		39		(14)		65		87		(22)
Sales-type lease payments, net of income	3		3		—		9		13		(4)
Net interest and other financial costs(1)	(212)		(216)		4		(650)		(635)		(15)
Maintenance capital expenditures, net of reimbursements	(28)		(40)		12		(93)		(93)		—
Equity method investment maintenance capital expenditures paid out	(4)		(4)		—		(11)		(10)		(1)
Other	(7)		11		(18)		(10)		28		(38)
DCF attributable to MPLX LP	1,373		1,264		109		3,956		3,711		245
Preferred unit distributions	(25)		(33)		8		(76)		(96)		20
DCF attributable to GP and LP unitholders	$	1,348	$	1,231	$	117	$	3,880	$	3,615	$	265

(1)    Excludes gain/loss on extinguishment of debt and amortization of deferred financing costs.

Three months ended September 30, 2023 compared to three months ended September 30, 2022

Total revenues and other income decreased $489 million in the third quarter of 2023 compared to the same period of 2022. The decrease was driven by a contract modification that resulted in a non-cash gain on sales-type lease of $509 million in the third quarter of 2022. In addition, product sales revenue decreased as a result of lower NGL prices during the third quarter of 2023 as compared to the same period of 2022. The decrease was partially offset by rate escalations and higher throughput across the business and a $34 million increase in income from equity method investments primarily due to higher throughput.

Purchased product costs decreased $66 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to lower NGL prices of $276 million, partially offset by higher NGL volumes of $157 million and a change of $53 million due to changes in the fair value of an embedded derivative in a natural gas purchase commitment.

Purchases - related parties increased $78 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to Garyville Incident response costs of $63 million and increased employee costs from MPC.

Interest expense, net of amounts capitalized increased $6 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to refinancing maturing debt with fixed rate debt at higher interest rates in 2022 and 2023 in addition to taking on incremental debt in order to finance the redemption of the 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series B preferred units”) in the first quarter of 2023. Other financial costs, net also benefited from higher interest earned during the third quarter of 2023. Refer to the Liquidity and Capital Resources section for further information.

Nine months ended September 30, 2023 compared to nine months ended September 30, 2022

Total revenues and other income decreased $636 million in the first nine months of 2023 compared to the same period of 2022. The decrease was driven by a contract modification that resulted in a non-cash gain on sales-type lease of $509 million in the third quarter of 2022 in addition to lower product sales revenue as a result of lower NGL prices during the first nine months of

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2023 as compared to the same period of 2022. The decrease was partially offset by rate escalations and higher throughput across the business and a $103 million increase in income from equity method investments primarily due to higher throughput.

Cost of revenues increased $42 million and rental cost of sales (including related party) decreased $61 million in the first nine months of 2023 compared to the same period of 2022. These offsetting variances reflect the modification of a gathering and compression agreement in the third quarter of 2022 (“Third-Party Lease Modification”), which resulted in a change in the presentation of expenses from rental cost of sales to cost of revenues.

Purchased product costs decreased $436 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to lower NGL prices of $826 million, partially offset by higher volumes of $329 million and a change of $61 million due to changes in the fair value of an embedded derivative in a natural gas purchase commitment.

Purchases - related parties increased $126 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to Garyville Incident response costs of $63 million, higher volumes and pricing on associated related-party purchased product costs, and higher transportation costs.

Depreciation and amortization decreased $18 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to lower depreciation as a result of the derecognition of fixed assets in connection with the Third-Party Lease Modification in the third quarter of 2022. This decrease was partially offset by depreciation on new assets placed in service after the third quarter of 2022.

General and administrative expenses increased $32 million in the first nine months of 2023 compared to the same period of 2022 due to increased costs from MPC, primarily higher employee costs, and other miscellaneous expenses.

Interest expense, net of amounts capitalized increased $46 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to refinancing debt with fixed rate debt at higher interest rates in 2022 and 2023 in addition to taking on incremental debt in order to finance the redemption of the Series B preferred units in the first quarter of 2023. Other financial costs, net also benefited from higher interest earned during 2023. Refer to the Liquidity and Capital Resources section for further information.

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Segment Results

We classify our business in the following reportable segments: L&S and G&P. We evaluate the performance of our segments using Segment Adjusted EBITDA. Segment Adjusted EBITDA represents Adjusted EBITDA attributable to the reportable segments. Amounts included in net income and excluded from Segment Adjusted EBITDA include: (i) depreciation and amortization; (ii) interest and other financial costs; (iii) income/(loss) from equity method investments; (iv) distributions and adjustments related to equity method investments; (v) gain on sales-type leases; (vi) impairment expense; (vii) noncontrolling interests; and (viii) other adjustments, as applicable. These items are either: (i) believed to be non-recurring in nature; (ii) not believed to be allocable or controlled by the segment; or (iii) are not tied to the operational performance of the segment.

The tables below present information about Segment Adjusted EBITDA for the reported segments for the three and nine months ended September 30, 2023 and September 30, 2022.

L&S Segment

Third Quarter L&S Segment Financial Highlights (in millions)

	Three Months Ended September 30,						Nine Months Ended September 30,
(In millions)	2023		2022		Variance		2023		2022		Variance
Service revenue	$	1,130	$	1,038	$	92	$	3,223	$	3,031	$	192
Rental income	216		210		6		638		593		45
Product related revenue	6		4		2		14		15		(1)
Sales-type lease revenue	129		118		11		379		343		36
Income from equity method investments	95		72		23		248		183		65
Other income	15		8		7		47		42		5
Total segment revenues and other income	1,591		1,450		141		4,549		4,207		342
Cost of revenues	158		160		(2)		451		460		(9)
Purchases - related parties	341		265		76		848		762		86
Depreciation and amortization	130		128		2		399		387		12
General and administrative expenses	60		48		12		160		134		26
Other taxes	32		19		13		71		60		11
Total costs and expenses	721		620		101		1,929		1,803		126
Segment income from operations	870		830		40		2,620		2,404		216
Segment Adjusted EBITDA	1,091		969		122		3,139		2,839		300
Capital expenditures	73		80		(7)		251		238		13
Investments in unconsolidated affiliates(1)	$	7	$	12	$	(5)	$	23	$	90	$	(67)

(1)    The nine months ended September 30, 2022 includes a contribution of $60 million to a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL, to fund our share of a debt repayment by the joint venture.

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Three months ended September 30, 2023 compared to three months ended September 30, 2022

Service revenue increased $92 million in the third quarter of 2023 compared to the same period of 2022. This was primarily driven by higher pipeline tariff rates, increased pipeline throughput, and $15 million from refining logistics fee escalations.

Sales-type lease revenue increased $11 million in the third quarter of 2023 compared to the same period of 2022. This was due to an increase of $5 million from changes in the presentation of revenue between service revenue, rental income and sales-type lease revenue as a result of modifications to agreements with MPC, with the remainder being attributable to fee escalations.

Income from equity method investments increased $23 million in the third quarter of 2023 compared to the same period of 2022. This was primarily driven by increased throughput on equity method investment pipeline systems.

Purchases - related parties increased $76 million in the third quarter of 2023 compared to the same period of 2022, primarily due to Garyville Incident response costs of $63 million and increased employee costs from MPC.

General and administrative expenses increased $12 million in the first nine months of 2023 compared to the same period of 2022, due to increased costs from MPC, primarily higher employee costs, as well as other miscellaneous increases.

Nine months ended September 30, 2023 compared to nine months ended September 30, 2022

Service revenue increased $192 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to higher pipeline tariff rates and increased pipeline throughput, and $32 million from refining logistics fee escalations. These increases were partially offset by a decrease of $41 million from changes in the presentation of revenue between service revenue, rental income and sales-type lease revenue driven by modifications to agreements with MPC.

Rental income increased $45 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to an increase of $18 million from changes in the presentation of revenue between service revenue, rental income and sales-type lease revenue driven by modifications to agreements with MPC. The remaining increase was primarily due to the escalation of storage fees.

Sales-type lease revenue increased $36 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to an increase of $23 million from changes in the presentation of revenue between service revenue, rental income and sales-type lease revenue as a result of modifications to agreements with MPC, as well as an increase of $12 million from refining logistics due to fee escalations.

Income from equity method investments increased $65 million in the first nine months of 2023 compared to the same period of 2022. This was primarily driven by increased throughput on equity method investment pipeline systems.

Purchases - related parties increased $86 million in the first nine months of 2023 compared to the same period of 2022, primarily due to Garyville Incident response costs of $63 million and increased employee costs from MPC.

General and administrative expenses increased $26 million in the first nine months of 2023 compared to the same period of 2022, due to increased costs from MPC, primarily higher employee costs, as well as other miscellaneous increases.

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L&S Operating Data

	Three Months Ended  September 30,				Nine Months Ended  September 30,
	2023		2022		2023		2022
L&S
Pipeline throughput (mbpd)
Crude oil pipelines	3,911		3,596		3,796		3,551
Product pipelines	1,975		2,169		2,027		2,125
Total pipelines	5,886		5,765		5,823		5,676
Average tariff rates ($ per barrel)(1)
Crude oil pipelines	$	0.99	$	0.93	$	0.95	$	0.91
Product pipelines	0.99		0.80		0.88		0.80
Total pipelines	$	0.99	$	0.88	$	0.93	$	0.86
Terminal throughput (mbpd)	3,228		3,026		3,167		3,023
Marine Assets (number in operation)(2)
Barges	305		296		305		296
Towboats	27		23		27		23

(1)     Average tariff rates calculated using pipeline transportation revenues divided by pipeline throughput barrels. Transportation revenues include tariff and other fees, which may vary by region and nature of services provided.

(2)     Represents total at end of period.

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G&P Segment

Third Quarter G&P Segment Financial Highlights (in millions)

(1)     The 2022 amount includes a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

	Three Months Ended September 30,						Nine Months Ended September 30,
(In millions)	2023		2022		Variance		2023		2022		Variance
Service revenue	$	549	$	537	$	12	$	1,620	$	1,528	$	92
Rental income	52		66		(14)		155		239		(84)
Product related revenue	598		742		(144)		1,629		2,263		(634)
Sales-type lease revenue	34		28		6		101		28		73
Income from equity method investments	64		53		11		190		152		38
Other income(1)	24		525		(501)		71		534		(463)
Total segment revenues and other income	1,321		1,951		(630)		3,766		4,744		(978)
Cost of revenues	237		243		(6)		656		666		(10)
Purchased product costs	474		540		(66)		1,234		1,670		(436)
Purchases - related parties	101		99		2		312		272		40
Depreciation and amortization	171		174		(3)		508		538		(30)
General and administrative expenses	42		40		2		120		114		6
Other taxes	12		11		1		31		37		(6)
Total costs and expenses	1,037		1,107		(70)		2,861		3,297		(436)
Segment Adjusted EBITDA	505		502		3		1,507		1,482		25
Capital expenditures	151		146		5		417		336		81
Investments in unconsolidated affiliates	$	6	$	30	$	(24)	$	67	$	108	$	(41)

(1)     The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

Three months ended September 30, 2023 compared to three months ended September 30, 2022

Service revenue increased $12 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to higher volumes and higher throughput fee rates in the Marcellus.

Rental income decreased $14 million and sales-type lease revenue increased $6 million in the third quarter of 2023 compared to the same period of 2022. The net decrease was primarily due to a contract modification that decreased the amount of revenue allocated to Rental income in Southern Appalachia beginning in the first quarter of 2023, partially offset by higher volumes and higher throughput fee rates.

Product related revenue decreased $144 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to lower NGL prices across all regions of $310 million, partially offset by higher volumes in the Southwest of $175 million.

Income from equity method investments increased $11 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to higher volumes associated with several of our joint ventures in the Marcellus and Utica. Additionally,

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our joint venture in the Southwest region added processing capacity in the fourth quarter of 2022 driving higher volumes over the prior period.

Other income decreased $501 million in the third quarter of 2023 compared to the same period of 2022 due primarily to a non-cash gain on lease reclassification of $509 million in the third quarter of 2022.

Purchased product costs decreased $66 million in the third quarter of 2023 compared to the same period of 2022. This was primarily due to lower NGL prices in the Southwest and Southern Appalachia of $276 million, partially offset by higher NGL volumes in the Southwest of $157 million and a change of $53 million due to changes in the fair value of an embedded derivative in a natural gas purchase commitment.

Nine months ended September 30, 2023 compared to nine months ended September 30, 2022

Service revenue increased $92 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to higher volumes and higher throughput fee rates in the Marcellus and Rockies.

Rental income decreased $84 million and sales-type lease revenue increased $73 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to changes in the presentation of revenue between rental income and sales-type lease revenue as a result of the Third-Party Lease Modification in the third quarter of 2022. In addition, a contract modification decreased the amount of revenue allocated to Rental income in Southern Appalachia beginning in the first quarter 2023.

Product related revenue decreased $634 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to lower prices across all regions of $958 million, partially offset by higher volumes in the Southwest of $322 million.

Income from equity method investments increased $38 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to higher volumes associated with several of our joint ventures in the Marcellus and Utica. Additionally, our joint venture in the Southwest region added processing capacity in the fourth quarter of 2022 driving higher volumes over the prior period.

Other income decreased $463 million in the first nine months of 2023 compared to the same period of 2022 due primarily to a non-cash gain on lease reclassification of $509 million in the third quarter of 2022 partially offset by the impact of asset disposals year over year.

Purchased product costs decreased $436 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to lower NGL prices of $826 million in the Southwest and Southern Appalachia, partially offset by higher volumes in the Southwest of $329 million and a change of $61 million due to changes in the fair value of an embedded derivative in a natural gas purchase commitment.

Purchases - related parties increased $40 million in the first nine months of 2023 compared to the same period of 2022. The increase is attributable to higher volumes and pricing on associated related-party purchased product costs in the Rockies and higher transportation costs from increased throughput in the Southwest.

Depreciation and amortization decreased $30 million in the first nine months of 2023 compared to the same period of 2022. This was primarily due to lower depreciation as a result of the derecognition of fixed assets in connection with the Third-Party Lease Modification in the third quarter of 2022. This decrease was partially offset by depreciation on new assets placed in service after the third quarter of 2022.

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G&P Operating Data

        

(1)     Other includes Southern Appalachia, Bakken and Rockies Operations.

	MPLX LP(1)		MPLX LP Operated(2)
	Three Months Ended  September 30,		Three Months Ended  September 30,
	2023	2022	2023	2022
G&P
Gathering Throughput (MMcf/d)
Marcellus Operations	1,376	1,325	1,376	1,325
Utica Operations	—	—	2,375	2,381
Southwest Operations	1,302	1,362	1,742	1,642
Bakken Operations	160	147	160	147
Rockies Operations	490	452	604	588
Total gathering throughput	3,328	3,286	6,257	6,083
Natural Gas Processed (MMcf/d)
Marcellus Operations	4,187	4,060	5,803	5,535
Utica Operations	—	—	557	518
Southwest Operations	1,405	1,502	1,744	1,666
Southern Appalachian Operations	207	205	207	205
Bakken Operations	159	130	159	130
Rockies Operations	491	462	491	462
Total natural gas processed	6,449	6,359	8,961	8,516
C2 + NGLs Fractionated (mbpd)
Marcellus Operations(3)	546	496	546	496
Utica Operations(3)	—	—	34	30
Southern Appalachian Operations	10	12	10	12
Bakken Operations	20	21	20	21
Rockies Operations	3	3	3	3
Total C2 + NGLs fractionated(4)	579	532	613	562

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	MPLX LP(1)		MPLX LP Operated(2)
	Nine Months Ended  September 30,		Nine Months Ended  September 30,
	2023	2022	2023	2022
G&P
Gathering Throughput (MMcf/d)
Marcellus Operations	1,353	1,308	1,353	1,308
Utica Operations	—	—	2,387	2,048
Southwest Operations	1,345	1,367	1,775	1,605
Bakken Operations	159	147	159	147
Rockies Operations	463	424	584	556
Total gathering throughput	3,320	3,246	6,258	5,664
Natural Gas Processed (MMcf/d)
Marcellus Operations	4,107	4,021	5,683	5,503
Utica Operations	—	—	533	488
Southwest Operations	1,442	1,446	1,771	1,616
Southern Appalachian Operations	219	220	219	220
Bakken Operations	157	138	157	138
Rockies Operations	472	436	472	436
Total natural gas processed	6,397	6,261	8,835	8,401
C2 + NGLs Fractionated (mbpd)
Marcellus Operations(3)	533	478	533	478
Utica Operations(3)	—	—	31	28
Southern Appalachian Operations	10	11	10	11
Bakken Operations	19	21	19	21
Rockies Operations	3	3	3	3
Total C2 + NGLs fractionated(4)	565	513	596	541

	Three Months Ended  September 30,				Nine Months Ended  September 30,
	2023		2022		2023		2022
Pricing Information
Natural Gas NYMEX HH ($ per MMBtu)	$	2.66	$	7.91	$	2.58	$	6.67
C2 + NGL Pricing ($ per gallon)(5)	$	0.68	$	1.01	$	0.69	$	1.11

(1)    This column represents operating data for entities that have been consolidated into the MPLX financial statements.

(2)    This column represents operating data for entities that have been consolidated into the MPLX financial statements as well as operating data for MPLX-operated equity method investments.

(3)    Entities within the Marcellus and Utica Operations jointly own the Hopedale fractionation complex. Hopedale throughput is included in the Marcellus and Utica Operations and represent each region’s utilization of the complex.

(4)    Purity ethane makes up approximately 246 mbpd and 210 mbpd of MPLX LP consolidated total fractionated products for the three months ended September 30, 2023 and September 30, 2022, respectively, and approximately 240 mbpd and 195 mbpd of total fractionated products for the nine months ended September 30, 2023 and September 30, 2022, respectively. Purity ethane makes up approximately 254 mbpd and 217 mbpd of MPLX LP Operated total fractionated products for the three months ended September 30, 2023 and September 30, 2022, respectively, and approximately 246 mbpd and 200 mbpd of total fractionated products for the nine months ended September 30, 2023 and September 30, 2022, respectively.

(5)    C2 + NGL pricing based on Mont Belvieu prices assuming an NGL barrel of approximately 35 percent ethane, 35 percent propane, six percent Iso-Butane, 12 percent normal butane and 12 percent natural gasoline.

Seasonality

The volume of crude oil and refined products transported and stored utilizing our assets is affected by the level of supply and demand for crude oil and refined products in the markets served directly or indirectly by our assets. The majority of effects of seasonality on the L&S segment’s revenues are mitigated through the use of fee-based transportation and storage services agreements with MPC that include minimum volume commitments.

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In our G&P segment, we experience minimal impacts from seasonal fluctuations which impact the demand for natural gas and NGLs and the related commodity prices caused by various factors including variations in weather patterns from year to year. We are able to manage the seasonality impacts through the execution of our marketing strategy. Overall, our exposure to the seasonality fluctuations is limited due to the nature of our fee-based business.

Liquidity and Capital Resources

Cash Flows

Our cash and cash equivalents were $960 million at September 30, 2023 and $238 million at December 31, 2022. The change in cash and cash equivalents was due to the factors discussed below. Net cash provided by (used in) operating activities, investing activities and financing activities were as follows:

	Nine Months Ended  September 30,
(In millions)	2023		2022
Net cash provided by (used in):
Operating activities	$	3,908	$	3,651
Investing activities	(727)		(676)
Financing activities	(2,459)		(2,867)
Total	$	722	$	108

Net cash provided by operating activities increased $257 million in the first nine months of 2023 compared to the same period of 2022, primarily due to improved results from operations and favorable working capital changes during the first nine months of 2022 compared to the same period of 2023.

Net cash used in investing activities increased $51 million in the first nine months of 2023 compared to the same period of 2022, due to higher capital spending. The increase in the first nine months of 2023 was partially offset by higher contributions to equity method investments for the first half of 2022, which included a $60 million contribution to Dakota Access to fund our share of a scheduled debt repayment by the joint venture.

Net cash used in financing activities decreased $408 million in the first nine months of 2023 compared to the same period of 2022. The decrease was driven by net borrowings in the first half of 2023 as compared to net repayments in the first half of 2022, resulting in a decreased use of cash of $861 million. There were no unit repurchases in the first nine months of 2023 resulting in a $315 million lower use of cash as compared to the same period of 2022. The decrease in the use of cash was partially offset by the use of $600 million to redeem all of the outstanding Series B preferred units and by $171 million of higher distributions paid to unitholders during the first nine months of 2023 compared to the same period of 2022, as a result of the 10 percent increase in our base distribution effective for the third quarter of 2022.

Adjusted Free Cash Flow

The following table provides a reconciliation of Adjusted FCF and Adjusted FCF after distributions from net cash provided by operating activities for the three and nine months ended September 30, 2023 and September 30, 2022.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Net cash provided by operating activities(1)	$	1,244	$	1,039	$	3,908	$	3,651
Adjustments to reconcile net cash provided by operating activities to adjusted free cash flow
Net cash used in investing activities	(236)		(265)		(727)		(676)
Contributions from MPC	7		13		20		30
Distributions to noncontrolling interests	(11)		(10)		(30)		(29)
Adjusted free cash flow	1,004		777		3,171		2,976
Distributions paid to common and preferred unitholders	(799)		(755)		(2,419)		(2,248)
Adjusted free cash flow after distributions	$	205	$	22	$	752	$	728

(1)    The three months ended September 30, 2023 and September 30, 2022 include working capital builds of $56 million and $208 million, respectively. The nine months ended September 30, 2023 and September 30, 2022 include a working capital draw of $56 million and a working capital build of $60 million, respectively.

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Debt and Liquidity Overview

On February 9, 2023, MPLX issued $1.6 billion aggregate principal amount of notes, consisting of $1.1 billion principal amount of 5.00 percent senior notes due 2033 (the “2033 Senior Notes”) and $500 million principal amount of 5.65 percent senior notes due 2053 (the “2053 Senior Notes”). The 2033 Senior Notes were offered at a price to the public of 99.170 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023. The 2053 Senior Notes were offered at a price to the public of 99.536 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023.

On February 15, 2023, MPLX used $600 million of the net proceeds from the offering of the 2033 Senior Notes and 2053 Senior Notes described above to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the offering, and cash on hand, to redeem all of MPLX’s and MarkWest’s $1.0 billion aggregate principal amount of 4.50 percent senior notes due July 2023, at par, plus accrued and unpaid interest.

Our intention is to maintain an investment-grade credit profile. As of September 30, 2023, the credit ratings on our senior unsecured debt were as follows:

Rating Agency	Rating
Moody’s	Baa2 (stable outlook)
Standard & Poor’s	BBB (stable outlook)
Fitch	BBB (stable outlook)

The ratings reflect the respective views of the rating agencies and should not be interpreted as a recommendation to buy, sell or hold our securities. Although it is our intention to maintain a credit profile that supports an investment grade rating, there is no assurance that these ratings will continue for any given period of time. The ratings may be revised or withdrawn entirely by the rating agencies if, in their respective judgments, circumstances so warrant. A rating from one rating agency should be evaluated independently of ratings from other rating agencies.

The agreements governing our debt obligations do not contain credit rating triggers that would result in the acceleration of interest, principal or other payments solely in the event that our credit ratings are downgraded. However, any downgrades in the credit ratings of our senior unsecured debt ratings to below investment grade ratings could, among other things, increase the applicable interest rates and other fees payable under the MPLX Credit Agreement and may limit our ability to obtain future financing, including refinancing existing indebtedness.

Our liquidity totaled $4.5 billion at September 30, 2023 consisting of:

	September 30, 2023
(In millions)	Total Capacity		Outstanding Borrowings		Available Capacity
MPLX Credit Agreement(1)	$	2,000	$	—	$	2,000
MPC Loan Agreement	1,500		—		1,500
Total	$	3,500	$	—	3,500
Cash and cash equivalents					960
Total liquidity					$	4,460

(1)     Outstanding borrowings include less than $1 million in letters of credit outstanding under this facility.

We expect our ongoing sources of liquidity to include cash generated from operations and borrowings under our revolving credit facilities and access to capital markets. We believe that cash generated from these sources will be sufficient to meet our short-term and long-term funding requirements, including working capital requirements, capital expenditure requirements, contractual obligations, and quarterly cash distributions. Our material future obligations include interest on debt, payments of debt principal, purchase obligations including contracts to acquire plant, property and equipment, and our operating leases and service agreements. We may also, from time to time, repurchase our senior notes or preferred units in the open market, in tender offers, in privately negotiated transactions or otherwise in such volumes, at market prices and upon such other terms as we deem appropriate and execute unit repurchases under our unit repurchase program. MPC manages our cash and cash equivalents on our behalf directly with third-party institutions as part of the treasury services that it provides to us under our omnibus agreement. From time to time, we may also consider utilizing other sources of liquidity, including the formation of joint ventures or sales of non-strategic assets.

MPLX’s credit agreement (the “MPLX Credit Agreement”) matures in July 2027 and contains certain representations and warranties, affirmative and restrictive covenants and events of default that we consider to be usual and customary for an agreement of this type. The financial covenant requires MPLX to maintain a ratio of Consolidated Total Debt as of the end of each fiscal quarter to Consolidated EBITDA (both as defined in the MPLX Credit Agreement) for the prior four fiscal quarters of no greater than 5.0 to 1.0 (or 5.5 to 1.0 during the nine-month period following certain acquisitions). Consolidated EBITDA is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. Other

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covenants restrict us and/or certain of our subsidiaries from incurring debt, creating liens on assets and entering into transactions with affiliates. As of September 30, 2023, we were in compliance with this financial covenant with a ratio of Consolidated Total Debt to Consolidated EBITDA of 3.4 to 1.0, as well as all other covenants contained in the MPLX Credit Agreement.

Equity and Preferred Units Overview

Unit Repurchase Program

On August 2, 2022, we announced the board authorization for the repurchase of up to $1.0 billion of MPLX common units held by the public. The authorization has no expiration date. We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated unit repurchases, tender offers or open market solicitations for units, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time.

No units were repurchased during the nine months ended September 30, 2023. As of September 30, 2023, we had $846 million remaining under the repurchase authorization.

Redemption of the Series B Preferred Units

On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding Series B preferred units. MPLX paid unitholders the Series B preferred unit redemption price of $1,000 per unit. See Note 5 to the unaudited consolidated financial statements for more information.

Distributions on the Series B preferred units were payable semi-annually in arrears on the 15th day, or the first business day thereafter, of February and August of each year up to and including February 15, 2023. In accordance with these terms, MPLX made a final cash distribution of $21 million to Series B preferred unitholders on February 15, 2023, in conjunction with the redemption.

Distributions

We intend to pay a minimum quarterly distribution to the holders of our common units of $0.2625 per unit, or $1.05 per unit on an annualized basis, to the extent we have sufficient cash from our operations after the establishment of cash reserves and the payment of costs and expenses, including reimbursements of expenses to our general partner. The amount of distributions paid under our policy and the decision to make any distributions is determined by our general partner, taking into consideration the terms of our partnership agreement. Such minimum distribution would equate to $263 million per quarter, or $1,051 million per year, based on the number of common units outstanding at September 30, 2023.

On October 24, 2023, MPLX declared a cash distribution for the third quarter of 2023, totaling $851 million, or $0.850 per common unit. This distribution will be paid on November 13, 2023 to common unitholders of record on November 3, 2023. Although our partnership agreement requires that we distribute all of our available cash (as defined in the partnership agreement) each quarter, we do not otherwise have a legal obligation to distribute any particular amount per common unit. This rate will also be received by Series A preferred unitholders.

The allocation of total cash distributions is as follows for the three and nine months ended September 30, 2023 and September 30, 2022. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions, except per unit data)	2023		2022		2023		2022
Distribution declared:
Limited partner units - public	$	301	$	275	$	849	$	789
Limited partner units - MPC	550		502		1,554		1,415
Total LP distribution declared	851		777		2,403		2,204
Series A preferred units	25		23		71		65
Series B preferred units(1)	—		10		5		31
Total distribution declared	$	876	$	810	$	2,479	$	2,300
Quarterly cash distributions declared per limited partner common unit	$	0.850	$	0.775	$	2.400	$	2.185

(1)    The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Capital Expenditures

Our operations are capital intensive, requiring investments to expand, upgrade, enhance or maintain existing operations and to meet environmental and operational regulations. Our capital requirements consist of growth capital expenditures and maintenance capital expenditures. Growth capital expenditures are those incurred for acquisitions or capital improvements that we expect will increase our operating capacity for volumes gathered, processed, transported or fractionated, decrease operating expenses within our facilities or increase operating income over the long term. Examples of growth capital expenditures include costs to develop or acquire additional pipeline, terminal, processing or storage capacity. In general, growth capital includes costs that are expected to generate additional or new cash flow for MPLX. In contrast, maintenance capital expenditures are those made to replace partially or fully depreciated assets, to maintain the existing operating capacity of our assets and to extend their useful lives, or other capital expenditures that are incurred in maintaining existing system volumes and related cash flows.

MPLX’s initial capital investment plan for 2023 totals $950 million, net of reimbursements, which includes growth capital of $800 million and maintenance capital of $150 million. Growth capital expenditures and investments in affiliates during the nine months ended September 30, 2023 were primarily for gas processing plants and gathering projects in the Marcellus and Permian basins, as well as additions to our brown water marine fleet. We continuously evaluate our capital plan and make changes as conditions warrant.

Our capital expenditures are shown in the table below:

	Nine Months Ended  September 30,
(In millions)	2023		2022
Capital expenditures:
Growth capital expenditures	$	555	$	451
Growth capital reimbursements(1)	(119)		(70)
Investments in unconsolidated affiliates	90		198
Return of capital	—		(11)
Capitalized interest	(10)		(6)
Total growth capital expenditures(2)	516		562
Maintenance capital expenditures	113		123
Maintenance capital reimbursements	(20)		(30)
Capitalized interest	(1)		(1)
Total maintenance capital expenditures	92		92
Total growth and maintenance capital expenditures	608		654
Investments in unconsolidated affiliates(3)	(90)		(198)
Return of capital	—		11
Growth and maintenance capital reimbursements(4)	139		100
Increase in capital accruals	(6)		(39)
Capitalized interest	11		7
Additions to property, plant and equipment(3)	$	662	$	535

(1)    Growth capital reimbursements include reimbursements from customers and our Sponsor.

(2)    Total growth capital expenditures exclude $28 million of acquisitions for the nine months ended September 30, 2022.

(3)    Investments in unconsolidated affiliates and additions to property, plant and equipment are shown as separate lines within investing activities in the Consolidated Statements of Cash Flows.

(4)    Growth capital reimbursements are included in changes in deferred revenue within operating activities in the Consolidated Statements of Cash Flows. Maintenance capital reimbursements are included in the Contributions from MPC line within financing activities in the Consolidated Statements of Cash Flows.

Contractual Cash Obligations

As of September 30, 2023, our contractual cash obligations included debt, finance and operating lease obligations, purchase obligations for services and to acquire property, plant and equipment, and other liabilities. During the nine months ended September 30, 2023, our debt obligations increased by $600 million due to the issuance of senior notes and use of proceeds described above in Liquidity and Capital Resources-Debt and Liquidity Overview. There were no other material changes to our contractual obligations outside the ordinary course of business since December 31, 2022.

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Off-Balance Sheet Arrangements

Off-balance sheet arrangements comprise those arrangements that may potentially impact our liquidity, capital resources and results of operations, even though such arrangements are not recorded as liabilities under GAAP. Our off-balance sheet arrangements are limited to guarantees that are described in Note 15 of the unaudited consolidated financial statements and indemnities as disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022.

Although these arrangements serve a variety of our business purposes, we are not dependent on them to maintain our liquidity and capital resources, and we are not aware of any circumstances that are reasonably likely to cause the off-balance sheet arrangements to have a material adverse effect on our liquidity and capital resources.

Transactions with Related Parties

At September 30, 2023, MPC owned our non-economic general partnership interest and held approximately 65 percent of our outstanding common units.

We provide MPC with crude oil and product pipeline based on regulated tariff/contracted rates, as well as storage, terminal, fuels distribution, and inland marine transportation services based on contracted rates. We also have agreements with MPC under which we receive fees for operating MPC’s retained pipeline assets, providing management services for the marine business, and operating certain of MPC’s equity method investments. MPC provides us with certain services related to information technology, engineering, legal, accounting, treasury, human resources and other administrative services under employee services and omnibus services agreements.

The below table shows the percentage of Total revenues and other income as well as Total costs and expenses with MPC:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
	2023		2022		2023		2022
Total revenues and other income(1)	49	%	46	%	50	%	46	%
Total costs and expenses	29	%	24	%	28	%	24	%

(1)    2022 periods exclude gain on sales-type leases.

For further discussion of agreements and activity with MPC and related parties see Item 1. Business in our Annual Report on Form 10-K for the year ended December 31, 2022 and Note 4 to the unaudited consolidated financial statements in this report.

Environmental Matters and Compliance Costs

We have incurred and may continue to incur substantial capital, operating and maintenance, and remediation expenditures as a result of environmental laws and regulations. If these expenditures, as with all costs, are not ultimately reflected in the prices of our products and services, our operating results will be adversely affected. We believe that substantially all of our competitors must comply with similar environmental laws and regulations. However, the specific impact on each competitor may vary depending on a number of factors, including, but not limited to, the age and location of its operating facilities.

As previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022, actual expenditures may vary as the number and scope of environmental projects are revised as a result of improved technology or changes in regulatory requirements. There have been no material changes to our environmental matters and compliance costs since our Annual Report on Form 10-K for the year ended December 31, 2022.

Critical Accounting Estimates

As of September 30, 2023, there have been no significant changes to our critical accounting estimates since our Annual Report on Form 10-K for the year ended December 31, 2022.

Accounting Standards Not Yet Adopted

We have not identified any recent accounting pronouncements that are expected to have a material impact on our financial condition, results of operations or cash flows upon adoption. Accounting standards are discussed in Note 2 of the unaudited consolidated financial statements.

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Item 3. Quantitative and Qualitative Disclosures about Market Risk

We are exposed to market risks related to the volatility of commodity prices. We employ various strategies, including the use of commodity derivative instruments, to economically hedge the risks related to these price fluctuations. We are also exposed to market risks related to changes in interest rates. As of September 30, 2023, we did not have any open financial derivative instruments to hedge the economic risks related to interest rate fluctuations; however, we continually monitor the market and our exposure and may enter into these arrangements in the future.

Commodity Price Risk

The information about commodity price risk for the three and nine months ended September 30, 2023 does not differ materially from that discussed in Item 7A. Quantitative and Qualitative Disclosures about Market Risk of our Annual Report on Form 10-K for the year ended December 31, 2022.

Outstanding Derivative Contracts and Sensitivity Analysis

See Notes 9 and 10 to the unaudited consolidated financial statements for more information about the fair value measurement of our derivative instruments, as well as the amounts recorded in our consolidated balance sheets and statements of income. We do not designate any of our commodity derivative instruments as hedges for accounting purposes.

Our open derivative positions at September 30, 2023 will expire at various times through 2023. We prepared a sensitivity analysis to estimate our exposure to market risk associated with our derivative instruments. Based on our open net positions at September 30, 2023, a 10 percent change in quoted market prices of our derivative instruments, assuming all other factors remain constant, could change the fair value of our derivative instruments and Income before income taxes by $1.0 million. This analysis may differ from actual results.

Interest Rate Risk and Sensitivity Analysis

Sensitivity analysis of the effect of a hypothetical 100-basis-point change in interest rates on outstanding third-party debt, excluding finance leases, is provided in the following table. Fair value of cash and cash equivalents, receivables, accounts payable and accrued interest approximate carrying value and are relatively insensitive to changes in interest rates due to the short-term maturity of the instruments. Accordingly, these instruments are excluded from the table.

(In millions)	Fair Value as of September 30, 2023(1)		Change in Fair Value(2)		Change in Income Before Income Taxes for the Three Months Ended September 30, 2023(3)
Outstanding debt
Fixed-rate	$	17,922	$	1,363	N/A
Variable-rate(4)	$	—	$	—	$	—

(1)    Fair value was based on market prices, where available, or current borrowing rates for financings with similar terms and maturities.

(2)    Assumes a 100-basis-point decrease in the weighted average yield-to-maturity at September 30, 2023.

(3)    Assumes a 100-basis-point change in interest rates. The change to income before income taxes was based on the weighted average balance of all outstanding variable-rate debt for the nine months ended September 30, 2023.

(4)    MPLX had no outstanding borrowings on the MPLX Credit Agreement as of September 30, 2023.

At September 30, 2023, our portfolio of third‑party debt consisted of fixed-rate instruments and outstanding borrowings, if any, under the MPLX Credit Agreement. The fair value of our fixed-rate debt is relatively sensitive to interest rate fluctuations. Our sensitivity to interest rate declines and corresponding increases in the fair value of our debt portfolio unfavorably affects our results of operations and cash flows only when we elect to repurchase or otherwise retire fixed-rate debt at prices above carrying value. Interest rate fluctuations generally do not impact the fair value of borrowings under our MPLX Credit Agreement, but may affect our results of operations and cash flows.

See Note 9 in the unaudited consolidated financial statements for additional information on the fair value of our debt.

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Item 4. Controls and Procedures

Disclosure Controls and Procedures

An evaluation of the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended) was carried out under the supervision and with the participation of management, including the chief executive officer and chief financial officer of our general partner. Based upon that evaluation, the chief executive officer and chief financial officer of our general partner concluded that the design and operation of these disclosure controls and procedures were effective as of September 30, 2023, the end of the period covered by this report.

Changes in Internal Control Over Financial Reporting

During the quarter ended September 30, 2023, there were no changes in our internal control over financial reporting that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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Part II – Other Information

Item 1. Legal Proceedings

We are the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. While it is possible that an adverse result in one or more of the lawsuits or proceedings in which we are a defendant could be material to us, based upon current information and our experience as a defendant in other matters, we believe that these lawsuits and proceedings, individually or in the aggregate, will not have a material adverse effect on our consolidated results of operations, financial position or cash flows.

Item 103 of Regulation S-K promulgated by the SEC requires disclosure of certain environmental matters when a governmental authority is a party to the proceedings and such proceedings involve potential monetary sanctions, unless we reasonably believe that the matter will result in no monetary sanctions, or in monetary sanctions, exclusive of interest and costs, of less than a specified threshold. We use a threshold of $1 million for this purpose.

Except as described below, there have been no material changes to the legal matters previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022, or in our Quarterly Report on Form 10-Q for the quarters ended March 31, 2023 and June 30, 2023.

Dakota Access Pipeline

As reported in our Annual Report on Form 10-K for the year ended December 31, 2022, MPLX holds a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The Army Corps has not provided a definitive date as to when a final decision would be issued.

We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system.

If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of September 30, 2023, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.

Edwardsville Incident

As reported in our Annual Report on Form 10-K for the year ended December 31, 2022, in March 2022, the State of Illinois brought an action in Madison County Circuit Court in Illinois against Marathon Pipe Line LLC (“MPL”), an indirect wholly owned subsidiary of MPLX, asserting various violations and demanding a permanent injunction and civil penalties in connection with a release of crude oil on the Wood River to Patoka 22" line near Edwardsville, Illinois in March 2022. In September 2023, the U.S. Department of Justice and EPA confirmed they will be pursuing federal enforcement for alleged Clean Water Act violations arising from this incident as well as other pipeline releases. We cannot currently estimate the amount of any civil penalty or the timing of the resolution of this matter but do not believe any civil penalty will have a material impact on our consolidated results of operations, financial position or cash flows.

Item 1A. Risk Factors

There have been no material changes from the risk factors previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022.

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Item 5. Other Information

During the quarter ended September 30, 2023, no director or officer (as defined in Rule 16a-1(f) promulgated under the Exchange Act) of MPLX adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement” (as each term is defined in Item 408 of Regulation S-K).

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Item 6. Exhibits

		Incorporated by Reference From
Exhibit Number	Exhibit Description	Form	Exhibit	Filing Date	SEC File No.	Filed Herewith	Furnished Herewith
3.1	Certificate of Limited Partnership of MPLX LP	S-1	3.1	7/2/2012	333-182500
3.2	Amendment to the Certificate of Limited Partnership of MPLX LP	S-1/A	3.2	10/9/2012	333-182500
3.3	Sixth Amended and Restated Agreement of Limited Partnership of MPLX LP, dated as of February 1, 2021	8-K	3.1	2/3/2021	001-35714
10.1	MPLX GP LLC Amended and Restated Non-Management Director Compensation Policy and Director Equity Award Terms					X
31.1	Certification of Chief Executive Officer pursuant to Rule 13a-14 and 15d-14 under the Securities Exchange Act of 1934					X
31.2	Certification of Chief Financial Officer pursuant to Rule 13a-14 and 15d-14 under the Securities Exchange Act of 1934					X
32.1	Certification of Chief Executive Officer pursuant to 18 U.S.C. Section 1350						X
32.2	Certification of Chief Financial Officer pursuant to 18 U.S.C. Section 1350						X
101.INS	XBRL Instance Document: The instance document does not appear in the interactive data file because its XBRL tags are embedded within the Inline XBRL document.
101.SCH	Inline XBRL Taxonomy Extension Schema Document.					X
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document.					X
101.DEF	Inline XBRL Taxonomy Extension Definition Linkbase Document.					X
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document.					X
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document.					X
104	Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101).

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	MPLX LP
	By:	MPLX GP LLC
		Its general partner
Date: October 31, 2023	By:	/s/ Kelly D. Wright
		Kelly D. Wright
		Vice President and Controller of MPLX GP LLC (the general partner of MPLX LP)

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EX-10.1

Exhibit 10.1

MPLX GP LLC AMENDED AND RESTATED NON-MANAGEMENT DIRECTOR COMPENSATION POLICY AND DIRECTOR EQUITY AWARD TERMS

Effective October 1, 2023

Directors of MPLX GP LLC (the “Company”) who are not employed by the Company or one of its subsidiaries or affiliates (“Non-Management Directors”) shall receive compensation for their services on the Board of Directors of the Company (the “Board”) and related committees as set forth below.

The equity awards set forth herein will be made from the MPLX LP 2018 Incentive Compensation Plan or any successor plan approved by the Board (the “Plan”). This Policy shall apply to those awards made in denominations of common units and other similar awards granted to Non-Management Directors under the Plan.

The Plan and this Policy are intended to conform to the requirements of Section 409A of the Internal Revenue Code of 1986, as amended, and the Department of Treasury Regulations and other interpretive guidance issued thereunder (“Section 409A”), and, in all respects, shall be administered and construed in accordance with such requirements.

This Policy became effective upon the filing of a Form S-8 Registration Statement with the U.S. Securities and Exchange Commission to register common units of MPLX LP authorized to be issued under the Plan.

The Non-Management Director Compensation Package of the Company is as follows:

MPLX GP LLC Non-Management Director Compensation Package
Annual Board Retainer (Cash)	$100,000
Annual Director Deferred Phantom Unit Equity Award	$125,000
Total Annual Compensation Package – Exclusive of Chair Retainers	$225,000
Audit Committee Annual Chair Retainer (Cash)	$25,000
Conflicts Committee Annual Chair Retainer (Cash)	$25,000
Lead Director Annual Retainer (Cash)	$25,000

Members of the Conflicts Committee also receive a meeting fee in the amount of $1,500 per meeting for each Conflicts Committee meeting such member attends in a calendar year in excess of six meetings.

Both the Deferred Phantom Unit Equity Awards (“Phantom Units”) and the Cash Retainer component of Non-Management Director Compensation shall be awarded or paid, as the case may be, to each Non-Management Director on a quarterly basis, with each installment being equal to one-fourth of the

annualized amount set forth above. At the commencement of each calendar quarter, each Non-Management Director then in office will automatically receive an award under the Plan of a number of Phantom Units, including any fractional Phantom Units, determined as set forth herein and such awards will bear a grant date of the first trading day of such quarter. All equity awards under this Policy shall be automatically deferred until the receiving Non-Management Director separates from service on the Board. The Board, Committee Chair and Lead Director Cash Retainer component of Non-Management Director Compensation will be paid on a quarterly basis, with a check cut or direct deposit made at the inception of each quarter in the amount one-fourth of the annualized amount set forth above.

All expenses incurred by Non-Management Directors to attend meetings of the Board and related committees, and otherwise attend to Company business will either be fully paid or reimbursed by the Company.

Any new Non-Management Director who commences service during any calendar quarter and after the beginning of such calendar quarter shall receive a pro-rated Phantom Unit award for such calendar quarter, with the grant date of such Phantom Unit award being the date of commencement of service on the Board, and a pro-rated quarterly Board, Committee and other Cash Retainer payment, as applicable. In each case, pro-ration will be calculated based on the number of days that the Non-Management Director is expected to serve on the Board during such calendar quarter relative to the total number of days in such calendar quarter.

Effective October 1, 2023, the number of Phantom Units subject to each quarterly award shall be determined by dividing $31,250, or such other pro-rated amount as applicable, by the closing market price of MPLX LP common units as reported on the Consolidated Tape System on the grant date. The number of Phantom Units, including any fractional Phantom Units, will be recorded in an unfunded and unsecured deferred compensation bookkeeping account in the Non-Management Director’s name. To the extent cash distributions are paid to common unit holders of MPLX LP, additional Phantom Units, including any fractional Phantom Units, will accrue within the Director’s deferred compensation account in recognition of the value of such distributions and shall be subject to the same automatic deferral and restrictions, terms and conditions as the underlying Phantom Units.

Each Phantom Unit held in a Non-Management Director’s accumulated deferred compensation account will increase or decrease in value by the same amount and with the same frequency as the fair market value of a common unit of MPLX LP.

In the event of a reorganization, recapitalization, unit equity split, dividend, combination of equity units, merger, consolidation, rights offering or any other change in the legal entity structure, the number and kind of Phantom Units credited to each Non-Management Director’s accumulated deferred compensation account shall be adjusted accordingly.

The deferred Phantom Units shall vest in full upon the Non-Management Director’s separation from service on the Board. Upon a Non-Management Director’s separation from service on the Board for any reason other than death, the Phantom Units in the Non-Management Director’s account shall be settled

on the first day of the calendar month following the expiration of 45 days after such separation from service and such Non-Management Director will receive unrestricted issued MPLX LP common units in place of the total accumulated Phantom Units in his or her deferred compensation account balance.

Upon a Non-Management Director’s separation from service on the Board on account of death, the Phantom Units in his or her deferred compensation account shall be fully vested. Unrestricted issued MPLX LP common units will be transferred to the Non-Management Director’s designated beneficiary either in February of the year following such Non-Management Director’s death or on the first day of the calendar month following the expiration of 45 days after the Non-Management Director’s death, whichever is earlier. If there is no valid beneficiary designation by the Non-Management Director, or if the designated beneficiary or beneficiaries fail to survive the Non-Management Director or otherwise fail to take the unrestricted issued MPLX LP common units, the Non-Management Director’s beneficiary shall be the Non-Management Director’s surviving spouse or, if there is no surviving spouse, the Non-Management Director’s estate. Otherwise, Non-Management Directors may not sell, transfer, assign, pledge or otherwise encumber any portion of the Phantom Units and any attempt to sell, transfer, assign, pledge or encumber any portion of the Phantom Units shall have no effect. In order to ensure that MPLX GP LLC Board members bear the full risks of unit ownership, MPLX GP LLC Directors are prohibited from hedging transactions related to MPLX LP common units or pledging or creating a security interest in any MPLX LP common units.

Each Phantom Unit award made under this Policy to Non-Management Directors shall be subject to the terms and conditions of this Policy and the Plan, and this Policy and the Plan shall serve as the governing award agreement and shall evidence the grants and awards made pursuant to this Policy. The Board may amend or terminate this Policy at any time as set forth under the Plan other than an amendment which would cause any outstanding award or distribution to fail to comply with Section 409A. This Policy is subject to the terms and conditions of the Plan and any terms or conditions not specifically set forth or provided within this Policy shall be governed by the Plan, including but not limited to the provisions required to comply with Section 409A, in particular: “separation from service” as used under this Policy shall have the same meaning as used under Section 409A; and those provisions regarding distributions to “specified employees” under Section 409A shall apply to distributions under this Policy.

Notwithstanding any provision of this Policy to the contrary, to the extent any reimbursement or in-kind benefit provided under this Policy is nonqualified deferred compensation within the meaning of Section 409A: (1) the amount of expenses eligible for reimbursement, or in-kind benefits provided, during a calendar year may not affect the expenses eligible for reimbursement, or in-kind benefits to be provided, in any other taxable year; (2) the reimbursement of an eligible expense must be made on or before the last day of the calendar year following the calendar year in which the expense was incurred; and (3) the right to reimbursement or in-kind benefits is not subject to liquidation or exchange for another benefit.

EX-31.1

Exhibit 31.1

CERTIFICATION PURSUANT TO SECTION 302 OF

THE SARBANES-OXLEY ACT OF 2002

I, Michael J. Hennigan, certify that:

1.I have reviewed this report on Form 10-Q of MPLX LP;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5.The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: October 31, 2023	/s/ Michael J. Hennigan
	Michael J. Hennigan
	Chairman of the Board, President and Chief Executive Officer of MPLX GP LLC (the general partner of MPLX LP)

EX-31.2

Exhibit 31.2

CERTIFICATION PURSUANT TO SECTION 302 OF

THE SARBANES-OXLEY ACT OF 2002

I, John J. Quaid, certify that:

1.I have reviewed this report on Form 10-Q of MPLX LP;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5.The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: October 31, 2023	/s/ John J. Quaid
	John J. Quaid
	Executive Vice President and Chief Financial Officer of MPLX GP LLC (the general partner of MPLX LP)

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of MPLX LP (the “Partnership”) on Form 10-Q for the quarter ended September 30, 2023 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Michael J. Hennigan, Chairman of the Board, President and Chief Executive Officer of MPLX GP LLC, the general partner of the Partnership, certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1)The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Partnership.

Date: October 31, 2023

/s/ Michael J. Hennigan

Michael J. Hennigan

Chairman of the Board, President and Chief Executive Officer of MPLX GP LLC (the general partner of MPLX LP)

EX-32.2

Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of MPLX LP (the “Partnership”) on Form 10-Q for the quarter ended September 30, 2023 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, John J. Quaid, Executive Vice President and Chief Financial Officer of MPLX GP LLC, the general partner of the Partnership, certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1)The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Partnership.

Date: October 31, 2023

/s/ John J. Quaid

John J. Quaid

Executive Vice President and Chief Financial Officer of MPLX GP LLC (the general partner of MPLX LP)

XML

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 27, 2023
Cover [Abstract]
Entity Central Index Key	0001552000
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-35714
Entity Registrant Name	MPLX LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0005456
Entity Address, Address Line One	200 E. Hardin Street,
Entity Address, City or Town	Findlay,
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45840
City Area Code	419
Local Phone Number	421-2414
Title of 12(b) Security	Common Units Representing Limited Partnership Interests
Trading Symbol	MPLX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Partnership, Units Outstanding		1,001,217,044

XML

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Sales-type lease revenue		$ 34	$ 28	$ 101	$ 28
Sales-type lease revenue - related parties		129	118	379	343
Income from equity method investments		159	125	438	335
Total revenues and other income		2,912	3,401	8,315	8,951
Costs and Expenses, Related Party		442	364	1,160	1,034
Depreciation and amortization	[1]	301	302	907	925
General and administrative expenses		102	88	280	248
Other taxes		44	30	102	97
Total costs and expenses		1,758	1,727	4,790	5,100
Operating Income (Loss)		1,154	1,674	3,525	3,851
Interest expense, net of amounts capitalized		223	217	673	627
Other financial costs, net		2	19	28	59
Income before income taxes		929	1,438	2,824	3,160
Provision for income taxes		1	1	2	6
Net income		928	1,437	2,822	3,154
Less: Net income attributable to noncontrolling interests		10	9	28	26
Net income attributable to MPLX LP	[2]	918	1,428	2,794	3,128
Limited partners' interest in net income attributable to MPLX LP		$ 893	$ 1,395	$ 2,718	$ 3,032
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.89	$ 1.36	$ 2.70	$ 2.97
Common - diluted		$ 0.89	$ 1.36	$ 2.70	$ 2.97
Weighted average limited partner units outstanding:
Common - basic		1,001	1,010	1,001	1,012
Common - diluted		1,001	1,011	1,001	1,013
Nonrelated Party [Member]
Rental income		$ 61	$ 75	$ 181	$ 268
Other Income		7	505	28	494
Rental cost of sales		20	22	60	101
Related Party [Member]
Rental income		207	201	612	564
Other Income		32	28	90	82
Rental cost of sales		8	10	24	44
General and administrative expenses		72	60	197	173
Affiliated Entity
Related-party interest and other financial costs		0	0	0	5
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		641	627	1,881	1,758
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		1,038	948	2,962	2,801
Service, Other [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		75	83	214	324
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		478	617	1,274	1,812
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		51	46	155	142
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		367	371	1,023	981
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		474	540	1,234	1,670
Series A Preferred Stock [Member]
Net income attributable to MPLX LP	[2]	26	41	80	89
Dividends, Preferred Stock		25	23	71	65
Series B Preferred Stock [Member]
Net income attributable to MPLX LP	[2]		10	5	31
Dividends, Preferred Stock		0	10	5	31
Common Unit-holders Public
Net income attributable to MPLX LP	[2]	$ 892	$ 1,377	$ 2,709	$ 3,008

[1] Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

[2] Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

XML

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net income	$ 928	$ 1,437	$ 2,822	$ 3,154
Other Comprehensive Income (Loss), Net of Tax	0	0	4	9
Comprehensive income	928	1,437	2,826	3,163
Less comprehensive income attributable to:
Noncontrolling interests	10	9	28	26
Comprehensive income attributable to MPLX LP	$ 918	$ 1,428	$ 2,798	$ 3,137

XML

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents	$ 960	$ 238
Receivables, net	833	737
Inventories	154	148
Other current assets	30	53
Total current assets	2,736	1,905
Equity method investments	4,099	4,095
Property, plant and equipment, net	18,620	18,848
Intangibles, net	609	705
Goodwill	7,645	7,645
Right of use assets, net	271	283
Other noncurrent assets	966	959
Total assets	36,120	35,665
Liabilities
Accounts payable	132	224
Accrued liabilities	332	269
Accrued property, plant and equipment	140	128
Long-term debt due within one year	1	988
Accrued interest payable	187	237
Operating lease liabilities	48	46
Total current liabilities	1,399	2,401
Long-term deferred revenue	295	219
Long-term debt	20,417	18,808
Deferred income taxes	12	13
Long-term operating lease liabilities	219	230
Other long-term liabilities	119	142
Total liabilities	22,804	22,151
Commitments and contingencies (see Note 15)
Temporary Equity, Carrying Amount, Attributable to Parent	970	968
Equity
Preferred Units, Preferred Partners' Capital Accounts	0	611
Accumulated other comprehensive loss	(4)	(8)
Total MPLX LP partners’ capital	12,110	12,309
Noncontrolling interests	236	237
Total equity	12,346	12,546
Total liabilities, preferred units and equity	36,120	35,665
Related Party [Member]
Assets
Receivables, net	599	610
Current assets - related parties	759	729
Other current assets	6	3
Right of use assets, net	227	228
Noncurrent assets - related parties	1,174	1,225
Liabilities
Operating lease liabilities	1	1
Other current liabilities	387	343
Long-term deferred revenue	117	110
Long-term liabilities - related parties	343	338
Equity
Limited Partners' Capital Account	3,581	3,293
Nonrelated Party [Member]
Liabilities
Other current liabilities	172	166
Long-term deferred revenue	292	216
Equity
Limited Partners' Capital Account	$ 8,533	$ 8,413

XML

Consolidated Balance Sheets (Parenthetical) - shares	Sep. 30, 2023	Dec. 31, 2022
Units Outstanding	1,001,217,044	1,001,020,616
Series B Preferred Stock [Member]
Preferred Units, Issued	0	600,000
Preferred Units, Outstanding	0	600,000
Series A Preferred Stock [Member]
Preferred Units, Issued	30,000,000	30,000,000
Preferred Units, Outstanding	30,000,000	30,000,000
Common Unit-holders Public | Nonrelated Party [Member]
Units issued	354,000,000	354,000,000
Units Outstanding	354,000,000	354,000,000
Common Unit-holders Public | Related Party [Member]
Units issued	647,000,000	647,000,000
Units Outstanding	647,000,000	647,000,000

XML

Consolidated Statements of Cash Flows - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022
Operating activities:
Net income		$ 2,822	$ 3,154
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs		42	55
Depreciation and amortization	[1]	907	925
Deferred income taxes		(1)	4
Gain on sales-type leases		0	(509)
(Gain)/loss on disposal of assets		(15)	23
Income from equity method investments		(438)	(335)
Distributions from unconsolidated affiliates		526	405
Change in fair value of derivatives		(3)	(62)
Changes in:
Receivables		(31)	(219)
Inventories		(15)	(7)
Accounts payable and accrued liabilities		(56)	49
Assets/liabilities - related parties		89	52
Right of use assets/operating lease liabilities		4	1
Deferred revenue		65	64
All other, net		12	51
Net cash provided by operating activities		3,908	3,651
Net Cash Provided by (Used in) Investing Activities [Abstract]
Additions to property, plant and equipment		(662)	(535)
Payments to Acquire Businesses, Net of Cash Acquired		0	28
Disposal of assets		25	74
Investments in unconsolidated affiliates		(90)	(198)
Distributions from unconsolidated affiliates - return of capital		0	11
Net cash used in investing activities		(727)	(676)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Long-term debt borrowings		1,589	3,379
Long-term debt - repayments		(1,001)	(2,202)
Debt issuance costs		15	29
Unit repurchases		0	(315)
Distributions to noncontrolling interests		(30)	(29)
Distributions to unitholders and general partner		(2,329)	(2,144)
Contributions from MPC		20	30
All other, net		(3)	(3)
Net cash used in financing activities		(2,459)	(2,867)
Net change in cash, cash equivalents and restricted cash		722	108
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		238	13
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance		960	121
Revolving Credit Facility
Net Cash Provided by (Used in) Financing Activities [Abstract]
Related party debt borrowings		0	2,824
Related party debt repayments		0	(4,274)
Series A Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Distributions to preferred unitholders		(69)	(63)
Series B Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Redemption of Series B preferred units		(600)	0
Distributions to preferred unitholders		$ (21)	$ (41)

[1] Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

XML

Consolidated Statements of Equity and Series A Preferred Units (Consolidated Statements of Equity) - USD ($) $ in Millions	Total	Common Unit-holders Public	Common Unit-holder MPC	Series B Preferred Unit-holders	Accumulated Other Comprehensive Loss	Non-controlling Interests
Beginning Balance at Dec. 31, 2021	$ 12,052	$ 8,579	$ 2,638	$ 611	$ (17)	$ 241
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	812	287	506	11	0	8
Unit repurchases	(100)	(100)	0	0	0	0
Distributions	(746)	(260)	(456)	(21)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(9)
Contributions	10	0	10	0	0	0
Other	8	(1)	0	0	9	0
Ending Balance at Mar. 31, 2022	12,036	8,505	2,698	601	(8)	240
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	863	304	540	10	0	9
Unit repurchases	(35)	(35)	0	0	0	0
Distributions	(724)	(257)	(457)	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(10)
Contributions	2	0	2	0	0	0
Other	2	1	1	0	0	0
Ending Balance at Jun. 30, 2022	12,144	8,518	2,784	611	(8)	239
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,414	502	893	10	0	9
Unit repurchases	(196)	(196)	0	0	0	0
Distributions	(744)	(258)	(456)	(20)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(10)
Contributions	55	0	55	0	0	0
Other	3	3	0	0	0	0
Ending Balance at Sep. 30, 2022	12,676	8,569	3,276	601	(8)	238
Beginning Balance at Dec. 31, 2022	12,546	8,413	3,293	611	(8)	237
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	929	323	592	5	0	9
Redemption of Series B preferred units	(600)	(2)	(3)	(595)	0	0
Distributions	(808)	(275)	(502)	(21)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(10)
Contributions	8	0	8	0	0	0
Other	5	0	0	0	4	1
Ending Balance at Mar. 31, 2023	12,080	8,459	3,388	0	(4)	237
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	919	322	588	0	0	9
Distributions	(785)	(274)	(502)	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(9)
Contributions	5	0	5	0	0	0
Other	2	1	1	0	0	0
Ending Balance at Jun. 30, 2023	12,221	8,508	3,480	0	(4)	237
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	903	297	596	0	0	10
Unit repurchases	0	0	0	0	0	0
Distributions	(787)	(274)	(502)	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders						(11)
Contributions	7	0	7	0	0	0
Other	2	2	0	0	0	0
Ending Balance at Sep. 30, 2023	$ 12,346	$ 8,533	$ 3,581	$ 0	$ (4)	$ 236

XML

Consolidated Statements of Equity and Series A Preferred Units (Temporary Equity) - USD ($) $ in Millions	Total	Series A Preferred Unit-holders
Beginning Balance at Dec. 31, 2021		$ 965
Temporary Equity, Net Income		21
Temporary Equity Account, Distributions		21
Ending Balance at Mar. 31, 2022		965
Temporary Equity, Net Income		21
Temporary Equity Account, Distributions		21
Ending Balance at Jun. 30, 2022		965
Temporary Equity, Net Income		23
Temporary Equity Account, Distributions		21
Ending Balance at Sep. 30, 2022		967
Beginning Balance at Dec. 31, 2022	$ 968	968
Temporary Equity, Net Income		23
Temporary Equity Account, Distributions		23
Ending Balance at Mar. 31, 2023		968
Temporary Equity, Net Income		23
Temporary Equity Account, Distributions		23
Ending Balance at Jun. 30, 2023		968
Temporary Equity, Net Income		25
Temporary Equity Account, Distributions		23
Ending Balance at Sep. 30, 2023	$ 970	$ 970

XML

Description of the Business and Basis of Presentation

9 Months Ended

Sep. 30, 2023

Accounting Policies [Abstract]

Business Description and Basis of Presentation

Description of the Business and Basis of Presentation

Description of the Business

MPLX LP is a diversified, large-cap master limited partnership formed by Marathon Petroleum Corporation that owns and operates midstream energy infrastructure and logistics assets, and provides fuels distribution services. We are engaged in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products and renewables; the gathering, processing and transportation of natural gas; and the transportation, fractionation, storage and marketing of NGLs. MPLX’s principal executive office is located in Findlay, Ohio. MPLX was formed on March 27, 2012 as a Delaware limited partnership and completed its initial public offering on October 31, 2012.

MPLX’s business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”), which relates primarily to crude oil, refined products, other hydrocarbon-based products and renewables; and Gathering and Processing (“G&P”), which relates primarily to natural gas and NGLs. See Note 7 for additional information regarding the operations and results of these segments.

Basis of Presentation

These interim consolidated financial statements are unaudited; however, in the opinion of MPLX’s management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules and regulations of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by GAAP for complete financial statements. Certain information derived from our audited annual financial statements, prepared in accordance with GAAP, has been condensed or omitted from these interim financial statements.

These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2022. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the full year.

MPLX’s consolidated financial statements include all majority-owned and controlled subsidiaries. For non-wholly owned consolidated subsidiaries, the interests owned by third parties have been recorded as Noncontrolling interests on the accompanying Consolidated Balance Sheets. Intercompany accounts and transactions have been eliminated. MPLX’s investments in which MPLX exercises significant influence but does not control and does not have a controlling financial interest are accounted for using the equity method. MPLX’s investments in VIEs in which MPLX exercises significant influence but does not control and is not the primary beneficiary are also accounted for using the equity method.

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Accounting Standards

9 Months Ended

Sep. 30, 2023

Accounting Standards Update and Change in Accounting Principle [Abstract]

Accounting Standards

Accounting Standards

Not Yet Adopted

ASU 2023-01, Leases (Topic 842): Common Control Arrangements

In March 2023, the FASB issued an ASU to amend certain provisions of ASC 842 that apply to arrangements between related parties under common control. The ASU amends the accounting for the amortization period of leasehold improvements in common-control leases for all entities and requires certain disclosures when the lease term is shorter than the useful life of the asset. This ASU is effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted. We do not expect the application of this ASU to have a material impact on our consolidated financial statements or financial disclosures.

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Investments and Noncontrolling Interest

9 Months Ended

Sep. 30, 2023

Equity Method Investments and Joint Ventures [Abstract]

Investments and Noncontrolling Interests

Investments and Noncontrolling Interests

The following table presents MPLX’s equity method investments at the dates indicated:

		Ownership as of	Carrying value at
		September 30,	September 30,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	174	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	238		236
LOOP LLC		41%	301		287
MarEn Bakken Company LLC(1)		25%	453		475
Minnesota Pipe Line Company, LLC		17%	174		178
Whistler Pipeline LLC		38%	212		211
Other(2)	X		298		269
Total L&S			1,850		1,833
G&P
Centrahoma Processing LLC		40%	117		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	339		335
MarkWest Torñado GP, L.L.C.	X	60%	310		306
MarkWest Utica EMG, L.L.C.	X	58%	684		669
Rendezvous Gas Services, L.L.C.	X	78%	130		137
Sherwood Midstream Holdings LLC	X	51%	116		125
Sherwood Midstream LLC	X	50%	507		512
Other(2)	X		46		47
Total G&P			2,249		2,262
Total			$	4,099	$	4,095

(1)    The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL.    

(2)    Some investments included within Other have also been deemed to be VIEs.

For those entities that have been deemed to be VIEs, neither MPLX nor any of its subsidiaries have been deemed to be the primary beneficiary due to voting rights on significant matters. While we have the ability to exercise influence through participation in the management committees which make all significant decisions, we have equal influence over each committee as a joint interest partner and all significant decisions require the consent of the other investors without regard to economic interest. As such, we have determined that these entities should not be consolidated and applied the equity method of accounting with respect to our investments in each entity.

MPLX’s maximum exposure to loss as a result of its involvement with equity method investments includes its equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of its compensation received for the performance of the operating services. MPLX did not provide any financial support to equity method investments that it was not contractually obligated to provide during the nine months ended September 30, 2023. See Note 15 for information on our Guarantees related to indebtedness of equity method investees.

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Related Party Agreements and Transactions

9 Months Ended

Sep. 30, 2023

Related Party Transactions [Abstract]

Related Party Agreements and Transactions

Related Party Agreements and Transactions

MPLX engages in transactions with both MPC and certain of its equity method investments as part of its normal business; however, transactions with MPC make up the majority of MPLX’s related party transactions. Transactions with related parties are further described below.

MPLX has various long-term, fee-based commercial agreements with MPC. Under these agreements, MPLX provides transportation, gathering, terminal, fuels distribution, marketing, storage, management, operational and other services to MPC. MPC has committed to provide MPLX with minimum quarterly throughput volumes on crude oil and refined products and other fees for storage capacity; operating and management fees; and reimbursements for certain direct and indirect costs. MPC has also committed to provide a fixed fee for 100 percent of available capacity for boats, barges and third-party chartered equipment under the marine transportation service agreement. MPLX also has a keep-whole commodity agreement with MPC under which MPC pays us a processing fee for NGLs related to keep-whole agreements and delivers shrink gas to the producers on our

behalf. We pay MPC a marketing fee in exchange for assuming the commodity risk. Additionally, MPLX has obligations to MPC for services provided to MPLX by MPC under omnibus and employee services-type agreements as well as other agreements.

During the second quarter of 2023, several terminal and storage services agreements with MPC were amended for certain items, including exercise of a five-year renewal option, with terms now extending to 2028.

Related Party Loan

MPLX is party to a loan agreement (the “MPC Loan Agreement”) with MPC. Under the terms of the MPC Loan Agreement, MPC extends loans to MPLX on a revolving basis as requested by MPLX and as agreed to by MPC. The borrowing capacity of the MPC Loan Agreement is $1.5 billion aggregate principal amount of all loans outstanding at any one time. The MPC Loan Agreement is scheduled to expire, and borrowings under the loan agreement are scheduled to mature and become due and payable, on July 31, 2024, provided that MPC may demand payment of all or any portion of the outstanding principal amount of the loan, together with all accrued and unpaid interest and other amounts (if any), at any time prior to maturity. Borrowings under the MPC Loan Agreement bear interest at one-month term SOFR adjusted upward by 0.10 percent plus 1.25 percent or such lower rate as would be applicable to such loans under the MPLX Credit Agreement as discussed in Note 11.

There was no activity on the MPC Loan Agreement for the nine months ended September 30, 2023.

Related Party Revenue

Related party sales to MPC primarily consist of crude oil and refined products pipeline based on tariff or contracted rates; storage, terminal and fuels distribution services based on contracted rates; and marine transportation services. Related party sales to MPC also consist of revenue related to volume deficiency credits.

MPLX also has operating agreements with MPC under which it receives a fee for operating MPC’s retained pipeline assets and a fixed annual fee for providing oversight and management services required to run the marine business. MPLX also receives management fee revenue for engineering, construction and administrative services for operating certain of its equity method investments. Amounts earned under these agreements are classified as Other income - related parties in the Consolidated Statements of Income.

Certain product sales to MPC and other related parties net to zero within the consolidated financial statements as the transactions are recorded net due to the terms of the agreements under which such product was sold. For the three and nine months ended September 30, 2023, these sales totaled $192 million and $540 million, respectively. For the three and nine months ended September 30, 2022, these sales totaled $235 million and $809 million, respectively.

Related Party Expenses

MPC charges MPLX for executive management services and certain general and administrative services provided to MPLX under the terms of our omnibus agreements (“Omnibus charges”) and for certain employee services provided to MPLX under employee services agreements (“ESA charges”). Omnibus charges and ESA charges are classified as Rental cost of sales - related parties, Purchases - related parties, or General and administrative expenses depending on the nature of the asset or activity with which the costs are associated. In addition to these agreements, MPLX purchases products from MPC, makes payments to MPC in its capacity as general contractor to MPLX, and has certain rent and lease agreements with MPC.

For the three and nine months ended September 30, 2023, General and administrative expenses incurred from MPC totaled $72 million and $197 million, respectively. For the three and nine months ended September 30, 2022, General and administrative expenses incurred from MPC totaled $60 million and $173 million, respectively.

Some charges incurred under the omnibus and employee service agreements are related to engineering services and are associated with assets under construction. These charges are added to Property, plant and equipment, net on the Consolidated Balance Sheets. For the three and nine months ended September 30, 2023, these charges totaled $28 million and $56 million, respectively. For the three and nine months ended September 30, 2022, these charges totaled $16 million and $54 million, respectively.

Related Party Assets and Liabilities

Assets and liabilities with related parties appearing in the Consolidated Balance Sheets are detailed in the table below. This table identifies the various components of related party assets and liabilities, including those associated with leases and deferred revenue on minimum volume commitments. If MPC fails to meet its minimum committed volumes, MPC will pay MPLX a deficiency payment based on the terms of the agreement. The deficiency amounts received under these agreements (excluding payments received under agreements classified as sales-type leases) are recorded as Current liabilities - related parties. In many cases, MPC may then apply the amount of any such deficiency payments as a credit for volumes in excess of its minimum volume commitment in future periods under the terms of the applicable agreements. MPLX recognizes related party revenues for the deficiency payments when credits are used for volumes in excess of minimum quarterly volume commitments, where it is

probable the customer will not use the credit in future periods or upon the expiration of the credits. The use or expiration of the credits is a decrease in Current liabilities - related parties. Deficiency payments under agreements that have been classified as sales-type leases are recorded as a reduction against the corresponding lease receivable. In addition, capital projects MPLX undertakes at the request of MPC are reimbursed in cash and recognized as revenue over the remaining term of the applicable agreements or in some cases, as a contribution from MPC.

(In millions)	September 30, 2023		December 31, 2022
Current assets - related parties
Receivables	$	599	$	610
Lease receivables	140		111
Prepaid	14		5
Other	6		3
Total	759		729
Noncurrent assets - related parties
Long-term lease receivables	811		883
Right of use assets	227		228
Unguaranteed residual asset	115		87
Long-term receivables	21		27
Total	1,174		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	312		262
Deferred revenue	74		80
Operating lease liabilities	1		1
Total	387		343
Long-term liabilities - related parties
Long-term operating lease liabilities	226		228
Long-term deferred revenue	117		110
Total	$	343	$	338

(1)    There were no borrowings outstanding on the MPC Loan Agreement as of September 30, 2023 or December 31, 2022.

Other Related Party Transactions

From time to time, MPLX may also sell to or purchase from related parties, assets and inventory at the lesser of average unit cost or net realizable value.

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Equity

9 Months Ended

Sep. 30, 2023

Equity [Abstract]

Equity

Equity

The changes in the number of common units during the nine months ended September 30, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	196,428
Balance at September 30, 2023	1,001,217,044

Unit Repurchase Program

On August 2, 2022, we announced the board authorization for the repurchase of up to $1 billion of MPLX common units held by the public. This unit repurchase authorization has no expiration date. We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated unit repurchases, tender offers or open market solicitations for units, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time.

No units were repurchased during the three or nine months ended September 30, 2023. As of September 30, 2023, we had $846 million remaining under the unit repurchase authorization.

Redemption of the Series B Preferred Units

On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series B preferred units”). MPLX paid unitholders the Series B preferred unit redemption price of $1,000 per unit.

Distributions on the Series B preferred units were payable semi-annually in arrears on the 15th day, or the first business day thereafter, of February and August of each year up to and including February 15, 2023. In accordance with these terms, MPLX made a final cash distribution of $21 million to Series B preferred unitholders on February 15, 2023, in conjunction with the redemption.

The changes in the Series B preferred unit balance during the nine months ended September 30, 2023 and September 30, 2022 are included in the Consolidated Statements of Equity within Series B preferred units.

Distributions

On October 24, 2023, MPLX declared a cash distribution for the third quarter of 2023, totaling $851 million, or $0.850 per common unit. This distribution will be paid on November 13, 2023 to common unitholders of record on November 3, 2023. This rate will also be received by Series A preferred unitholders.

Quarterly distributions for 2023 and 2022 are summarized below:

(Per common unit)	2023		2022
March 31,	$	0.775	$	0.705
June 30,	0.775		0.705
September 30,	$	0.850	$	0.775

The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three and nine months ended September 30, 2023 and September 30, 2022. Distributions, although earned, are not accrued until declared. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	851	$	777	$	2,403	$	2,204
Series A preferred unit distributions	25		23		71		65
Series B preferred unit distributions(1)	—		10		5		31
Total cash distributions declared	$	876	$	810	$	2,479	$	2,300

(1)    The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Net Income Per Limited Partner Unit

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Net Income Per Limited Partner Unit

Net Income Per Limited Partner Unit

Net income per unit applicable to common units is computed by dividing net income attributable to MPLX LP less income allocated to participating securities by the weighted average number of common units outstanding.

During the three and nine months ended September 30, 2023 and September 30, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units, and Series B preferred units and also had dilutive potential common units consisting of certain equity-based compensation awards. Potential common units omitted from the diluted earnings per unit calculation for the three and nine months ended September 30, 2023 and September 30, 2022 were less than 1 million.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Net income attributable to MPLX LP	$	918	$	1,428	$	2,794	$	3,128
Less: Distributions declared on Series A preferred units	25		23		71		65
Distributions declared on Series B preferred units	—		10		5		31
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	851		777		2,403		2,204
Undistributed net gain attributable to MPLX LP	$	42	$	618	$	315	$	828

	Three Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	851	$	25	$	876
Undistributed net gain attributable to MPLX LP	41		1		42
Net income attributable to MPLX LP(1)	$	892	$	26	$	918
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.89
Diluted	$	0.89

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Three Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	777	$	23	$	10	$	810
Undistributed net gain attributable to MPLX LP(1)	600		18		—		618
Net income attributable to MPLX LP(2)	$	1,377	$	41	$	10	$	1,428
Weighted average units outstanding:
Basic	1,010
Diluted	1,011
Net income attributable to MPLX LP per limited partner unit:
Basic	$	1.36
Diluted	$	1.36

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the three months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Nine Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,403	$	71	$	5	$	2,479
Undistributed net gain attributable to MPLX LP	306		9		—		315
Net income attributable to MPLX LP(1)	2,709		$	80	$	5	2,794
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	2,704					$	2,789
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.70
Diluted	$	2.70

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Nine Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,204	$	65	$	31	$	2,300
Undistributed net gain attributable to MPLX LP(1)	804		24		—		828
Net income attributable to MPLX LP(2)	$	3,008	$	89	$	31	$	3,128
Weighted average units outstanding:
Basic	1,012
Diluted	1,013
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.97
Diluted	$	2.97

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the nine months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

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Segment Information

9 Months Ended

Sep. 30, 2023

Segment Reporting [Abstract]

Segment Reporting Disclosure

Segment Information

MPLX’s chief operating decision maker (“CODM”) is the chief executive officer of its general partner. The CODM reviews MPLX’s discrete financial information, makes operating decisions, assesses financial performance and allocates resources on a type of service basis. MPLX has two reportable segments: L&S and G&P. Each of these segments is organized and managed based upon the nature of the products and services it offers.

•L&S – gathers, transports, stores and distributes crude oil, refined products, other hydrocarbon-based products and renewables. Also includes the operation of refining logistics, fuels distribution and inland marine businesses, terminals, rail facilities, and storage caverns.

•G&P – gathers, processes and transports natural gas; and transports, fractionates, stores and markets NGLs.

Our CODM evaluates the performance of our segments using Segment Adjusted EBITDA. Amounts included in net income and excluded from Segment Adjusted EBITDA include: (i) depreciation and amortization; (ii) interest and other financial costs; (iii) income/(loss) from equity method investments; (iv) distributions and adjustments related to equity method investments; (v) gain on sales-type leases; (vi) impairment expense; (vii) noncontrolling interests; and (viii) other adjustments, as applicable. These items are either: (i) believed to be non-recurring in nature; (ii) not believed to be allocable or controlled by the segment; or (iii) are

not tied to the operational performance of the segment. Assets by segment are not a measure used to assess the performance of the Partnership by our CODM and thus are not reported in our disclosures.

The tables below present information about revenues and other income, Segment Adjusted EBITDA, capital expenditures and investments in unconsolidated affiliates for our reportable segments:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
L&S
Service revenue	$	1,130	$	1,038	$	3,223	$	3,031
Rental income	216		210		638		593
Product related revenue	6		4		14		15
Sales-type lease revenue	129		118		379		343
Income from equity method investments	95		72		248		183
Other income	15		8		47		42
Total segment revenues and other income(1)	1,591		1,450		4,549		4,207
Segment Adjusted EBITDA(2)	1,091		969		3,139		2,839
Capital expenditures	73		80		251		238
Investments in unconsolidated affiliates	7		12		23		90
G&P
Service revenue	549		537		1,620		1,528
Rental income	52		66		155		239
Product related revenue	598		742		1,629		2,263
Sales-type lease revenue	34		28		101		28
Income from equity method investments	64		53		190		152
Other income(3)	24		525		71		534
Total segment revenues and other income(1)	1,321		1,951		3,766		4,744
Segment Adjusted EBITDA(2)	505		502		1,507		1,482
Capital expenditures	151		146		417		336
Investments in unconsolidated affiliates	$	6	$	30	$	67	$	108

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $564 million for the three and nine months ended September 30, 2023, respectively, and $175 million and $468 million for the three and nine months ended September 30, 2022, respectively. Third party revenues for the G&P segment were $1,248 million and $3,553 million for the three and nine months ended September 30, 2023, respectively, and $1,885 million and $4,551 million for the three and nine months ended September 30, 2022, respectively.

(2)    See below for the reconciliation from Segment Adjusted EBITDA to Net income.

(3)    The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

The table below provides a reconciliation of Segment Adjusted EBITDA for reportable segments to Net income.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,091	$	969	$	3,139	$	2,839
G&P Segment Adjusted EBITDA	505		502		1,507		1,482
Total reportable segments	1,596		1,471		4,646		4,321
Depreciation and amortization(1)	(301)		(302)		(907)		(925)
Gain on sales-type leases	—		509		—		509
Interest and other financial costs	(225)		(236)		(701)		(691)
Income from equity method investments	159		125		438		335
Distributions/adjustments related to equity method investments	(208)		(166)		(551)		(450)
Adjusted EBITDA attributable to noncontrolling interests	11		10		31		29
Garyville incident response costs(2)	(63)		—		(63)		—
Other(3)	(41)		26		(71)		26
Net income	$	928	$	1,437	$	2,822	$	3,154

(1)    Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

(2)    In August 2023, a naphtha release and resulting fire occurred at our Garyville Tank Farm resulting in the loss of four storage tanks with a combined shell capacity of 894 thousand barrels. We incurred $63 million of incident response costs during the three and nine months ended September 30, 2023.

(3)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

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Property, Plant and Equipment

9 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, Plant and Equipment

Property, plant and equipment with associated accumulated depreciation is shown below:

	September 30, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,633	$	3,919	$	8,714	$	12,416	$	3,554	$	8,862
G&P	13,844		3,938		9,906		13,495		3,509		9,986
Total	$	26,477	$	7,857	$	18,620	$	25,911	$	7,063	$	18,848

We capitalize interest as part of the cost of major projects during the construction period. Capitalized interest totaled $4 million and $11 million for the three and nine months ended September 30, 2023, respectively, and $2 million and $7 million for the three and nine months ended September 30, 2022, respectively.

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Fair Value Measurements

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Fair Value Disclosures

Fair Value Measurements

Fair Values – Recurring

The following table presents the impact on the Consolidated Balance Sheets of MPLX’s financial instruments carried at fair value on a recurring basis as of September 30, 2023 and December 31, 2022 by fair value hierarchy level.

	September 30, 2023				December 31, 2022
(In millions)	Asset		Liability		Asset		Liability
Commodity contracts (Level 2)
Other current assets / Other current liabilities	$	2	$	—	$	—	$	—
Embedded derivatives in commodity contracts (Level 3)
Other current assets / Other current liabilities	—		10		—		10
Other noncurrent assets / Other long-term liabilities	—		50		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	60	$	—	$	61

Level 2 instruments include over-the-counter fixed swaps to mitigate the price risk from our sales of propane. The swap valuations are based on observable inputs in the form of forward prices based on Mont Belvieu propane forward spot prices and contain no significant unobservable inputs.

Level 3 instruments relate to an embedded derivative liability for a natural gas purchase commitment embedded in a keep-whole processing agreement. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.61 to $1.66 per gallon with a weighted average of $0.79 per gallon and (2) a 100 percent probability of renewal for the five-year renewal term of the gas purchase commitment and related keep-whole processing agreement. Increases or decreases in the fractionation spread result in an increase or decrease in the fair value of the embedded derivative liability, respectively.

Changes in Level 3 Fair Value Measurements

The following table is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Beginning balance	$	(53)	$	(92)	$	(61)	$	(108)
Unrealized and realized (loss)/gain included in Net Income(1)	(10)		44		(7)		52
Settlements	3		2		8		10
Ending balance	$	(60)	$	(46)	$	(60)	$	(46)
The amount of total (loss)/gain for the period included in earnings attributable to the change in unrealized gain relating to liabilities still held at end of period	$	(9)	$	42	$	(6)	$	50

(1)     (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.

Fair Values – Reported

We believe the carrying value of our other financial instruments, including cash and cash equivalents, receivables, receivables from related parties, lease receivables, lease receivables from related parties, accounts payable, and payables to related parties, approximate fair value. MPLX’s fair value assessment incorporates a variety of considerations, including the duration of the instruments, MPC’s investment-grade credit rating, and the historical incurrence of and expected future insignificance of bad debt expense, which includes an evaluation of counterparty credit risk. The recorded value of the amounts outstanding under the bank revolving credit facility, if any, approximates fair value due to the variable interest rate that approximates current market rates. Derivative instruments are recorded at fair value, based on available market information (see Note 10).

The fair value of MPLX’s debt is estimated based on prices from recent trade activity and is categorized in Level 3 of the fair value hierarchy. The following table summarizes the fair value and carrying value of our third-party debt, excluding finance leases and unamortized debt issuance costs:

	September 30, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	17,922	$	20,536	$	18,095	$	19,905

(1)    Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring

Level 2 instruments include over-the-counter fixed swaps to mitigate the price risk from our sales of propane. The swap valuations are based on observable inputs in the form of forward prices based on Mont Belvieu propane forward spot prices and contain no significant unobservable inputs.

Level 3 instruments relate to an embedded derivative liability for a natural gas purchase commitment embedded in a keep-whole processing agreement. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.61 to $1.66 per gallon with a weighted average of $0.79 per gallon and (2) a 100 percent probability of renewal for the five-year renewal term of the gas purchase commitment and related keep-whole processing agreement. Increases or decreases in the fractionation spread result in an increase or decrease in the fair value of the embedded derivative liability, respectively.

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Derivative Financial Instruments

9 Months Ended

Sep. 30, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Disclosure

Derivatives

As of September 30, 2023, MPLX had the following outstanding commodity contracts that were executed to manage the price risk associated with sales of propane during 2023:

Derivative contracts not designated as hedging instruments	Financial Position	Notional Quantity
Propane (gallons)	Short	16,827,000

Embedded Derivative - MPLX has a natural gas purchase commitment embedded in a keep-whole processing agreement with a producer customer in the Southern Appalachian region expiring in December 2027. The customer has the unilateral option to extend the agreement for one five-year term through December 2032. For accounting purposes, the natural gas purchase commitment and the term extending option have been aggregated into a single compound embedded derivative. The probability of the customer exercising its option is determined based on assumptions about the customer’s potential business strategy decision points that may exist at the time they would elect whether to renew the contract. The changes in fair value of this compound embedded derivative are based on the difference between the contractual and index pricing, the probability of the producer customer exercising its option to extend, and the estimated favorability of these contracts compared to current market conditions. The changes in fair value are recorded in earnings through Purchased product costs in the Consolidated Statements of Income. For further information regarding the fair value measurement of derivative instruments, see Note 9. As of September 30, 2023 and December 31, 2022, the estimated fair value of this contract was a liability of $60 million and $61 million, respectively.

Certain derivative positions are subject to master netting agreements; therefore, MPLX has elected to offset derivative assets and liabilities that are legally permissible to be offset. As of September 30, 2023 and December 31, 2022, there were no derivative assets or liabilities that were offset in the Consolidated Balance Sheets.

We make a distinction between realized or unrealized gains and losses on derivatives. During the period when a derivative contract is outstanding, changes in the fair value of the derivative are recorded as an unrealized gain or loss. When a derivative contract matures or is settled, the previously recorded unrealized gain or loss is reversed, and the realized gain or loss of the contract is recorded. The impact of MPLX’s derivative contracts not designated as hedging instruments and the location of gains and losses recognized in the Consolidated Statements of Income is summarized below:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Product sales:
Realized gain	$	3	$	—	$	3	$	—
Unrealized (loss)/gain	(8)		—		2		—
Product sales derivative (loss)/gain	(5)		—		5		—
Purchased product costs:
Realized loss	(3)		(2)		(8)		(10)
Unrealized (loss)/gain	(7)		46		1		62
Purchased produce cost derivative (loss)/gain	(10)		44		(7)		52
Total derivative (loss)/gain included in Net income	$	(15)	$	44	$	(2)	$	52

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Debt

9 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Debt

Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	September 30, 2023		December 31, 2022
MPLX LP:
MPLX Credit Agreement	$	—	$	—
Fixed rate senior notes	20,657		20,046
Consolidated subsidiaries:
MarkWest	12		23
ANDX	31		31
Finance lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(125)		(117)
Unamortized discount	(164)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,417	$	18,808

Credit Agreement

MPLX’s credit agreement (the “MPLX Credit Agreement”) matures in July 2027 and, among other things, provides for a $2 billion unsecured revolving credit facility and letter of credit issuing capacity under the facility of up to $150 million. Letter of credit issuing capacity is included in, not in addition to, the $2 billion borrowing capacity. Borrowings under the MPLX Credit Agreement bear interest, at MPLX’s election, at either the Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin.

There was no activity on the MPLX Credit Agreement during the nine months ended September 30, 2023.

Fixed Rate Senior Notes

MPLX’s senior notes, including those issued by consolidated subsidiaries, consist of various series of senior notes maturing between 2024 and 2058 with interest rates ranging from 1.750 percent to 5.650 percent. Interest on each series of notes is payable semi-annually in arrears on various dates depending on the series of the notes.

On February 9, 2023, MPLX issued $1.6 billion aggregate principal amount of notes, consisting of $1.1 billion principal amount of 5.00 percent senior notes due 2033 (the “2033 Senior Notes”) and $500 million principal amount of 5.65 percent senior notes due 2053 (the “2053 Senior Notes”). The 2033 Senior Notes were offered at a price to the public of 99.170 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023. The 2053 Senior Notes were offered at a price to the public of 99.536 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023.

On February 15, 2023, MPLX used $600 million of the net proceeds from the offering of the 2033 Senior Notes and 2053 Senior Notes described above to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the offering, and cash on hand, to redeem all of MPLX’s and MarkWest’s $1.0 billion aggregate principal amount of 4.50 percent senior notes due July 2023, at par, plus accrued and unpaid interest. The redemption resulted in a loss of $9 million due to the immediate expense recognition of unamortized debt discount and issuance costs for the three months ended March 31, 2023, which is included on the Consolidated Statements of Income as Other financial costs, net.

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Revenue

9 Months Ended

Sep. 30, 2023

Revenue from Contract with Customer [Abstract]

Revenue

Revenue

Disaggregation of Revenue

The following tables represent a disaggregation of revenue for each reportable segment for the three and nine months ended September 30, 2023 and September 30, 2022:

	Three Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	97	$	544	$	641
Service revenue - related parties	1,033		5		1,038
Service revenue - product related	—		75		75
Product sales	2		476		478
Product sales - related parties	4		47		51
Total revenues from contracts with customers	$	1,136	$	1,147	2,283
Non-ASC 606 revenue(1)					629
Total revenues and other income					$	2,912

	Three Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	94	$	533	$	627
Service revenue - related parties	944		4		948
Service revenue - product related	—		83		83
Product sales	2		615		617
Product sales - related parties	2		44		46
Total revenues from contracts with customers	$	1,042	$	1,279	2,321
Non-ASC 606 revenue(1)					1,080
Total revenues and other income					$	3,401

	Nine Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	272	$	1,609	$	1,881
Service revenue - related parties	2,951		11		2,962
Service revenue - product related	—		214		214
Product sales	4		1,270		1,274
Product sales - related parties	10		145		155
Total revenues from contracts with customers	$	3,237	$	3,249	6,486
Non-ASC 606 revenue(1)					1,829
Total revenues and other income					$	8,315

	Nine Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	243	$	1,515	$	1,758
Service revenue - related parties	2,788		13		2,801
Service revenue - product related	—		324		324
Product sales	5		1,807		1,812
Product sales - related parties	10		132		142
Total revenues from contracts with customers	$	3,046	$	3,791	6,837
Non-ASC 606 revenue(1)					2,114
Total revenues and other income					$	8,951

(1)    Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.

Contract Balances

Our receivables are primarily associated with customer contracts. Payment terms vary by product or service type; however, the period between invoicing and payment is not significant. Included within the receivables are balances related to commodity sales on behalf of our producer customers, for which we remit the net sales price back to the producer customers upon completion of the sale. These balances are included in Receivables, net on the Consolidated Balance Sheets.

Under certain of our contracts, we recognize revenues in excess of billings which we present as contract assets. Contract assets typically relate to deficiency payments related to minimum volume commitments and aid in construction agreements where the revenue recognized and MPLX’s rights to consideration for work completed exceeds the amount billed to the customer. Contract assets are included in Other current assets and Other noncurrent assets on the Consolidated Balance Sheets.

Under certain of our contracts, we receive payments in advance of satisfying our performance obligations, which are recorded as contract liabilities. Contract liabilities, which we present as Deferred revenue and Long-term deferred revenue, typically relate to advance payments for aid in construction agreements and deferred customer credits associated with makeup rights and minimum volume commitments. Related to minimum volume commitments, breakage is estimated and recognized into service revenue in instances where it is probable the customer will not use the credit in future periods. We classify contract liabilities as current or long-term based on the timing of when we expect to recognize revenue.

The tables below reflect the changes in ASC 606 contract balances for the nine-month periods ended September 30, 2023 and September 30, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2023
Contract assets	$	21	$	(19)	$	—	$	2
Long-term contract assets	1		—		—		1
Deferred revenue	57		24		(31)		50
Deferred revenue - related parties	63		63		(72)		54
Long-term deferred revenue	216		76		—		292
Long-term deferred revenue - related parties	25		5		—		30
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2022
Contract assets	$	25	$	(9)	$	—	$	16
Long-term contract assets	2		—		—		2
Deferred revenue	56		40		(33)		63
Deferred revenue - related parties	60		79		(83)		56
Long-term deferred revenue	135		27		—		162
Long-term deferred revenue - related parties	31		(5)		—		26
Long-term contract liabilities	$	5	$	(1)	$	—	$	4

(1)     No significant revenue was recognized related to past performance obligations in the current periods.

Remaining Performance Obligations

The table below includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) as of September 30, 2023. The amounts presented below are generally limited to fixed consideration from contracts with customers that contain minimum volume commitments.

A significant portion of our future contracted revenue is excluded from the amounts presented below in accordance with ASC 606. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded from this disclosure. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less, or that are terminable by our customer with little or no termination penalties. Potential future performance obligations related to renewals that have not yet been exercised or are not certain of exercise are

excluded from the amounts presented below. Revenues classified as Rental income and Sales-type lease revenue are also excluded from this table.

(In billions)
2023	$	0.5
2024	2.0
2025	1.9
2026	1.7
2027	1.6
Thereafter	1.0
Total estimated revenue on remaining performance obligations	$	8.7

As of September 30, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $426 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 20 years. A portion of this amount is not disclosed in the table above as it is deemed variable consideration due to volume variability.

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Supplemental Cash Flow Information

9 Months Ended

Sep. 30, 2023

Supplemental Cash Flow Elements [Abstract]

Supplemental Cash Flow Information

Supplemental Cash Flow Information

	Nine Months Ended  September 30,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	724	$	642
Income taxes paid	4		2
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	8		—
Net transfers of property, plant and equipment to lease receivable	$	86	$	20

The Consolidated Statements of Cash Flows exclude changes to the Consolidated Balance Sheets that do not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures:

	Nine Months Ended  September 30,
(In millions)	2023		2022
Additions to property, plant and equipment	$	662	$	535
Increase in capital accruals	6		39
Total capital expenditures	$	668	$	574

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Leases, Codification Topic 842

9 Months Ended

Sep. 30, 2023

Leases [Abstract]

Lessor, Sales-type Leases

LeasesDuring the third quarter of 2022, the approved expansion of a gathering and compression system triggered the first assessment of the related third-party agreement under ASC 842. Similarly, an amendment to extend the term of our butane storage service agreement with MPC triggered the first assessment of the related-party agreement under ASC 842. As a result of the assessments during the third quarter of 2022, the leases were reclassified from operating leases to sales-type leases. Accordingly, the underlying property, plant and equipment, net, and associated deferred revenue, if any, were derecognized. The present value of the future lease payments and the unguaranteed residual value of the assets were recorded as a net investment in sales-type lease during the period.

The following presents the consolidated financial statement impact of the sales-type lease modifications discussed above. These transactions, including any related gains recognized in the Consolidated Statements of Income, were non-cash transactions.

	Three Months Ended  September 30, 2022
(In millions)	Related Party(1)		Third Party(2)
Lease receivables	$	79	$	914
Unguaranteed residual assets	6		63
Property, plant and equipment, net	(42)		(745)
Deferred revenue	—		277
Amount recognized on commencement date	$	43	$	509

(1)    The amount recognized on commencement date was recorded as a Contribution from MPC in the Consolidated Statements of Equity given the underlying agreements are between entities under common control.

(2)    The amount recognized on commencement date was recorded as a gain in Other income in the Consolidated Statements of Income.

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Commitments and Contingencies

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Commitments and Contingencies

MPLX is the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which MPLX has not recorded a liability, MPLX is unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings, discovery or court proceedings. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material.

Environmental Matters

MPLX is subject to federal, state and local laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites. Penalties may be imposed for non-compliance.

Accrued liabilities for remediation totaled $23 million at September 30, 2023 and $17 million December 31, 2022. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties, if any, that may be imposed.

MPLX is involved in environmental enforcement matters arising in the ordinary course of business. While the outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on its consolidated results of operations, financial position or cash flows.

Other Legal Proceedings

In July 2020, Tesoro High Plains Pipeline Company, LLC (“THPP”), a subsidiary of MPLX, received a Notification of Trespass Determination from the Bureau of Indian Affairs (“BIA”) relating to a portion of the Tesoro High Plains Pipeline that crosses the Fort Berthold Reservation in North Dakota. The notification demanded the immediate cessation of pipeline operations and assessed trespass damages of approximately $187 million. After subsequent appeal proceedings and in compliance with a new order issued by the BIA, in December 2020, THPP paid approximately $4 million in assessed trespass damages and ceased use of the portion of the pipeline that crosses the property at issue. In March 2021, the BIA issued an order purporting to vacate the BIA's prior orders related to THPP’s alleged trespass and direct the Regional Director of the BIA to reconsider the issue of THPP’s alleged trespass and issue a new order. In April 2021, THPP filed a lawsuit in the District of North Dakota against the United States of America, the U.S. Department of the Interior and the BIA (together, the “U.S. Government Parties”) challenging the March 2021 order purporting to vacate all previous orders related to THPP’s alleged trespass. On February 8, 2022, the U.S. Government Parties filed their answer and counterclaims to THPP’s suit claiming THPP is in continued trespass with respect to the pipeline and seeking disgorgement of pipeline profits from June 1, 2013 to present, removal of the pipeline and remediation. We intend to vigorously defend ourselves against these counterclaims.

MPLX is also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these other lawsuits and proceedings will not, individually or collectively, have a material adverse effect on its consolidated financial position, results of operations or cash flows.

Guarantees related to indebtedness of equity method investees

We hold a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The Army Corps has not provided a definitive date as to when a final decision would be issued.

In May 2021, the D.D.C. denied a renewed request for an injunction to shut down the pipeline while the EIS is being prepared. In June 2021, the D.D.C. issued an order dismissing without prejudice the tribes’ claims against the Dakota Access Pipeline. The litigation could be reopened or new litigation challenging the EIS, once completed, could be filed. The pipeline remains operational.

We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system.

If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of September 30, 2023, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.

Contractual Commitments and Contingencies

From time to time and in the ordinary course of business, MPLX and its affiliates provide guarantees of MPLX’s subsidiaries payment and performance obligations in the G&P segment. Certain natural gas processing and gathering arrangements require MPLX to construct new natural gas processing plants, natural gas gathering pipelines and NGL pipelines and contain certain fees and charges if specified construction milestones are not achieved for reasons other than force majeure. In certain cases, certain producers may have the right to cancel the processing arrangements if there are significant delays that are not due to force majeure. As of September 30, 2023, management does not believe there are any indications that MPLX will not be able to meet the construction milestones, that force majeure does not apply or that such fees and charges will otherwise be triggered.

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Pay vs Performance Disclosure - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net income attributable to MPLX LP	[1]	$ 918	$ 1,428	$ 2,794	$ 3,128

[1] Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

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Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the quarter ended September 30, 2023, no director or officer (as defined in Rule 16a-1(f) promulgated under the Exchange Act) of MPLX adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement” (as each term is defined in Item 408 of Regulation S-K).
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

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Description of the Business and Basis of Presentation Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Nature of Operations	We are engaged in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products and renewables; the gathering, processing and transportation of natural gas; and the transportation, fractionation, storage and marketing of NGLs. MPLX’s principal executive office is located in Findlay, Ohio. MPLX was formed on March 27, 2012 as a Delaware limited partnership and completed its initial public offering on October 31, 2012.MPLX’s business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”), which relates primarily to crude oil, refined products, other hydrocarbon-based products and renewables; and Gathering and Processing (“G&P”), which relates primarily to natural gas and NGLs. See Note 7 for additional information regarding the operations and results of these segments.
Basis of Accounting, Policy	These interim consolidated financial statements are unaudited; however, in the opinion of MPLX’s management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules and regulations of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by GAAP for complete financial statements. Certain information derived from our audited annual financial statements, prepared in accordance with GAAP, has been condensed or omitted from these interim financial statements.
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy	MPLX’s consolidated financial statements include all majority-owned and controlled subsidiaries. For non-wholly owned consolidated subsidiaries, the interests owned by third parties have been recorded as Noncontrolling interests on the accompanying Consolidated Balance Sheets. Intercompany accounts and transactions have been eliminated. MPLX’s investments in which MPLX exercises significant influence but does not control and does not have a controlling financial interest are accounted for using the equity method. MPLX’s investments in VIEs in which MPLX exercises significant influence but does not control and is not the primary beneficiary are also accounted for using the equity method.

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Net Income Per Limited Partner Unit Accounting Policy (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Earnings Per Unit, Policy	Net income per unit applicable to common units is computed by dividing net income attributable to MPLX LP less income allocated to participating securities by the weighted average number of common units outstanding.

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Investments and Noncontrolling Interests (Tables)

9 Months Ended

Sep. 30, 2023

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments

The following table presents MPLX’s equity method investments at the dates indicated:

		Ownership as of	Carrying value at
		September 30,	September 30,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	174	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	238		236
LOOP LLC		41%	301		287
MarEn Bakken Company LLC(1)		25%	453		475
Minnesota Pipe Line Company, LLC		17%	174		178
Whistler Pipeline LLC		38%	212		211
Other(2)	X		298		269
Total L&S			1,850		1,833
G&P
Centrahoma Processing LLC		40%	117		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	339		335
MarkWest Torñado GP, L.L.C.	X	60%	310		306
MarkWest Utica EMG, L.L.C.	X	58%	684		669
Rendezvous Gas Services, L.L.C.	X	78%	130		137
Sherwood Midstream Holdings LLC	X	51%	116		125
Sherwood Midstream LLC	X	50%	507		512
Other(2)	X		46		47
Total G&P			2,249		2,262
Total			$	4,099	$	4,095

(1)    The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL.    

(2)    Some investments included within Other have also been deemed to be VIEs.

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Related Party Agreements and Transactions (Tables)

9 Months Ended

Sep. 30, 2023

Related Party Transactions [Abstract]

Schedule of Related Party Transactions

Assets and liabilities with related parties appearing in the Consolidated Balance Sheets are detailed in the table below. This table identifies the various components of related party assets and liabilities, including those associated with leases and deferred revenue on minimum volume commitments. If MPC fails to meet its minimum committed volumes, MPC will pay MPLX a deficiency payment based on the terms of the agreement. The deficiency amounts received under these agreements (excluding payments received under agreements classified as sales-type leases) are recorded as Current liabilities - related parties. In many cases, MPC may then apply the amount of any such deficiency payments as a credit for volumes in excess of its minimum volume commitment in future periods under the terms of the applicable agreements. MPLX recognizes related party revenues for the deficiency payments when credits are used for volumes in excess of minimum quarterly volume commitments, where it is

probable the customer will not use the credit in future periods or upon the expiration of the credits. The use or expiration of the credits is a decrease in Current liabilities - related parties. Deficiency payments under agreements that have been classified as sales-type leases are recorded as a reduction against the corresponding lease receivable. In addition, capital projects MPLX undertakes at the request of MPC are reimbursed in cash and recognized as revenue over the remaining term of the applicable agreements or in some cases, as a contribution from MPC.

(In millions)	September 30, 2023		December 31, 2022
Current assets - related parties
Receivables	$	599	$	610
Lease receivables	140		111
Prepaid	14		5
Other	6		3
Total	759		729
Noncurrent assets - related parties
Long-term lease receivables	811		883
Right of use assets	227		228
Unguaranteed residual asset	115		87
Long-term receivables	21		27
Total	1,174		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	312		262
Deferred revenue	74		80
Operating lease liabilities	1		1
Total	387		343
Long-term liabilities - related parties
Long-term operating lease liabilities	226		228
Long-term deferred revenue	117		110
Total	$	343	$	338

(1)    There were no borrowings outstanding on the MPC Loan Agreement as of September 30, 2023 or December 31, 2022.

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Equity (Tables)

9 Months Ended

Sep. 30, 2023

Equity [Abstract]

Schedule of Stockholders Equity

The changes in the number of common units during the nine months ended September 30, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	196,428
Balance at September 30, 2023	1,001,217,044

Distributions Made to Limited Partner, by Distribution

The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three and nine months ended September 30, 2023 and September 30, 2022. Distributions, although earned, are not accrued until declared. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	851	$	777	$	2,403	$	2,204
Series A preferred unit distributions	25		23		71		65
Series B preferred unit distributions(1)	—		10		5		31
Total cash distributions declared	$	876	$	810	$	2,479	$	2,300

(1)    The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Net Income Per Limited Partner Unit (Tables)

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Schedule of Distributions By Partner By Class

MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units, and Series B preferred units and also had dilutive potential common units consisting of certain equity-based compensation awards. Potential common units omitted from the diluted earnings per unit calculation for the three and nine months ended September 30, 2023 and September 30, 2022 were less than 1 million.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Net income attributable to MPLX LP	$	918	$	1,428	$	2,794	$	3,128
Less: Distributions declared on Series A preferred units	25		23		71		65
Distributions declared on Series B preferred units	—		10		5		31
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	851		777		2,403		2,204
Undistributed net gain attributable to MPLX LP	$	42	$	618	$	315	$	828

Schedule of Net Income Per Unit, Basic and Diluted

	Three Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	851	$	25	$	876
Undistributed net gain attributable to MPLX LP	41		1		42
Net income attributable to MPLX LP(1)	$	892	$	26	$	918
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.89
Diluted	$	0.89

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Three Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	777	$	23	$	10	$	810
Undistributed net gain attributable to MPLX LP(1)	600		18		—		618
Net income attributable to MPLX LP(2)	$	1,377	$	41	$	10	$	1,428
Weighted average units outstanding:
Basic	1,010
Diluted	1,011
Net income attributable to MPLX LP per limited partner unit:
Basic	$	1.36
Diluted	$	1.36

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the three months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Nine Months Ended September 30, 2023
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,403	$	71	$	5	$	2,479
Undistributed net gain attributable to MPLX LP	306		9		—		315
Net income attributable to MPLX LP(1)	2,709		$	80	$	5	2,794
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	2,704					$	2,789
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.70
Diluted	$	2.70

(1)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

	Nine Months Ended September 30, 2022
(In millions, except per unit data)	Limited Partners’ Common Units		Series A Preferred Units		Series B Preferred Units		Total
Basic and diluted net income attributable to MPLX LP per unit
Net income attributable to MPLX LP:
Distributions declared	$	2,204	$	65	$	31	$	2,300
Undistributed net gain attributable to MPLX LP(1)	804		24		—		828
Net income attributable to MPLX LP(2)	$	3,008	$	89	$	31	$	3,128
Weighted average units outstanding:
Basic	1,012
Diluted	1,013
Net income attributable to MPLX LP per limited partner unit:
Basic	$	2.97
Diluted	$	2.97

(1)    The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the nine months ended September 30, 2022. See Note 14 for additional information.

(2)    Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

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Segment Information (Tables)

9 Months Ended

Sep. 30, 2023

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

The tables below present information about revenues and other income, Segment Adjusted EBITDA, capital expenditures and investments in unconsolidated affiliates for our reportable segments:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
L&S
Service revenue	$	1,130	$	1,038	$	3,223	$	3,031
Rental income	216		210		638		593
Product related revenue	6		4		14		15
Sales-type lease revenue	129		118		379		343
Income from equity method investments	95		72		248		183
Other income	15		8		47		42
Total segment revenues and other income(1)	1,591		1,450		4,549		4,207
Segment Adjusted EBITDA(2)	1,091		969		3,139		2,839
Capital expenditures	73		80		251		238
Investments in unconsolidated affiliates	7		12		23		90
G&P
Service revenue	549		537		1,620		1,528
Rental income	52		66		155		239
Product related revenue	598		742		1,629		2,263
Sales-type lease revenue	34		28		101		28
Income from equity method investments	64		53		190		152
Other income(3)	24		525		71		534
Total segment revenues and other income(1)	1,321		1,951		3,766		4,744
Segment Adjusted EBITDA(2)	505		502		1,507		1,482
Capital expenditures	151		146		417		336
Investments in unconsolidated affiliates	$	6	$	30	$	67	$	108

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $564 million for the three and nine months ended September 30, 2023, respectively, and $175 million and $468 million for the three and nine months ended September 30, 2022, respectively. Third party revenues for the G&P segment were $1,248 million and $3,553 million for the three and nine months ended September 30, 2023, respectively, and $1,885 million and $4,551 million for the three and nine months ended September 30, 2022, respectively.

(2)    See below for the reconciliation from Segment Adjusted EBITDA to Net income.

(3)    The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

Reconciliation of Other Significant Reconciling Items from Segments to Consolidated

The table below provides a reconciliation of Segment Adjusted EBITDA for reportable segments to Net income.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,091	$	969	$	3,139	$	2,839
G&P Segment Adjusted EBITDA	505		502		1,507		1,482
Total reportable segments	1,596		1,471		4,646		4,321
Depreciation and amortization(1)	(301)		(302)		(907)		(925)
Gain on sales-type leases	—		509		—		509
Interest and other financial costs	(225)		(236)		(701)		(691)
Income from equity method investments	159		125		438		335
Distributions/adjustments related to equity method investments	(208)		(166)		(551)		(450)
Adjusted EBITDA attributable to noncontrolling interests	11		10		31		29
Garyville incident response costs(2)	(63)		—		(63)		—
Other(3)	(41)		26		(71)		26
Net income	$	928	$	1,437	$	2,822	$	3,154

(1)    Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

(2)    In August 2023, a naphtha release and resulting fire occurred at our Garyville Tank Farm resulting in the loss of four storage tanks with a combined shell capacity of 894 thousand barrels. We incurred $63 million of incident response costs during the three and nine months ended September 30, 2023.

(3)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

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Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

Summary of Property, Plant and Equipment

Property, plant and equipment with associated accumulated depreciation is shown below:

	September 30, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,633	$	3,919	$	8,714	$	12,416	$	3,554	$	8,862
G&P	13,844		3,938		9,906		13,495		3,509		9,986
Total	$	26,477	$	7,857	$	18,620	$	25,911	$	7,063	$	18,848

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Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table presents the impact on the Consolidated Balance Sheets of MPLX’s financial instruments carried at fair value on a recurring basis as of September 30, 2023 and December 31, 2022 by fair value hierarchy level.

	September 30, 2023				December 31, 2022
(In millions)	Asset		Liability		Asset		Liability
Commodity contracts (Level 2)
Other current assets / Other current liabilities	$	2	$	—	$	—	$	—
Embedded derivatives in commodity contracts (Level 3)
Other current assets / Other current liabilities	—		10		—		10
Other noncurrent assets / Other long-term liabilities	—		50		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	60	$	—	$	61

Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation

The following table is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy.

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Beginning balance	$	(53)	$	(92)	$	(61)	$	(108)
Unrealized and realized (loss)/gain included in Net Income(1)	(10)		44		(7)		52
Settlements	3		2		8		10
Ending balance	$	(60)	$	(46)	$	(60)	$	(46)
The amount of total (loss)/gain for the period included in earnings attributable to the change in unrealized gain relating to liabilities still held at end of period	$	(9)	$	42	$	(6)	$	50

(1)     (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.

Fair Value Carrying Value by Balance Sheet Grouping

The following table summarizes the fair value and carrying value of our third-party debt, excluding finance leases and unamortized debt issuance costs:

	September 30, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	17,922	$	20,536	$	18,095	$	19,905

(1)    Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

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Derivative Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions

As of September 30, 2023, MPLX had the following outstanding commodity contracts that were executed to manage the price risk associated with sales of propane during 2023:

Derivative contracts not designated as hedging instruments	Financial Position	Notional Quantity
Propane (gallons)	Short	16,827,000

Schedule of Derivative Instruments, Gain (Loss)

The impact of MPLX’s derivative contracts not designated as hedging instruments and the location of gains and losses recognized in the Consolidated Statements of Income is summarized below:

	Three Months Ended  September 30,				Nine Months Ended  September 30,
(In millions)	2023		2022		2023		2022
Product sales:
Realized gain	$	3	$	—	$	3	$	—
Unrealized (loss)/gain	(8)		—		2		—
Product sales derivative (loss)/gain	(5)		—		5		—
Purchased product costs:
Realized loss	(3)		(2)		(8)		(10)
Unrealized (loss)/gain	(7)		46		1		62
Purchased produce cost derivative (loss)/gain	(10)		44		(7)		52
Total derivative (loss)/gain included in Net income	$	(15)	$	44	$	(2)	$	52

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Debt (Tables)

9 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Schedule of Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	September 30, 2023		December 31, 2022
MPLX LP:
MPLX Credit Agreement	$	—	$	—
Fixed rate senior notes	20,657		20,046
Consolidated subsidiaries:
MarkWest	12		23
ANDX	31		31
Finance lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(125)		(117)
Unamortized discount	(164)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,417	$	18,808

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Revenue (Tables)

9 Months Ended

Sep. 30, 2023

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue Table

The following tables represent a disaggregation of revenue for each reportable segment for the three and nine months ended September 30, 2023 and September 30, 2022:

	Three Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	97	$	544	$	641
Service revenue - related parties	1,033		5		1,038
Service revenue - product related	—		75		75
Product sales	2		476		478
Product sales - related parties	4		47		51
Total revenues from contracts with customers	$	1,136	$	1,147	2,283
Non-ASC 606 revenue(1)					629
Total revenues and other income					$	2,912

	Three Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	94	$	533	$	627
Service revenue - related parties	944		4		948
Service revenue - product related	—		83		83
Product sales	2		615		617
Product sales - related parties	2		44		46
Total revenues from contracts with customers	$	1,042	$	1,279	2,321
Non-ASC 606 revenue(1)					1,080
Total revenues and other income					$	3,401

	Nine Months Ended September 30, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	272	$	1,609	$	1,881
Service revenue - related parties	2,951		11		2,962
Service revenue - product related	—		214		214
Product sales	4		1,270		1,274
Product sales - related parties	10		145		155
Total revenues from contracts with customers	$	3,237	$	3,249	6,486
Non-ASC 606 revenue(1)					1,829
Total revenues and other income					$	8,315

	Nine Months Ended September 30, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	243	$	1,515	$	1,758
Service revenue - related parties	2,788		13		2,801
Service revenue - product related	—		324		324
Product sales	5		1,807		1,812
Product sales - related parties	10		132		142
Total revenues from contracts with customers	$	3,046	$	3,791	6,837
Non-ASC 606 revenue(1)					2,114
Total revenues and other income					$	8,951

(1)    Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.

Schedule of Contract with Customer, Contract Asset, Contract Liability, and Receivable

The tables below reflect the changes in ASC 606 contract balances for the nine-month periods ended September 30, 2023 and September 30, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2023
Contract assets	$	21	$	(19)	$	—	$	2
Long-term contract assets	1		—		—		1
Deferred revenue	57		24		(31)		50
Deferred revenue - related parties	63		63		(72)		54
Long-term deferred revenue	216		76		—		292
Long-term deferred revenue - related parties	25		5		—		30
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at September 30, 2022
Contract assets	$	25	$	(9)	$	—	$	16
Long-term contract assets	2		—		—		2
Deferred revenue	56		40		(33)		63
Deferred revenue - related parties	60		79		(83)		56
Long-term deferred revenue	135		27		—		162
Long-term deferred revenue - related parties	31		(5)		—		26
Long-term contract liabilities	$	5	$	(1)	$	—	$	4

(1)     No significant revenue was recognized related to past performance obligations in the current periods.

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction

The table below includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) as of September 30, 2023. The amounts presented below are generally limited to fixed consideration from contracts with customers that contain minimum volume commitments.

A significant portion of our future contracted revenue is excluded from the amounts presented below in accordance with ASC 606. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded from this disclosure. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less, or that are terminable by our customer with little or no termination penalties. Potential future performance obligations related to renewals that have not yet been exercised or are not certain of exercise are

excluded from the amounts presented below. Revenues classified as Rental income and Sales-type lease revenue are also excluded from this table.

(In billions)
2023	$	0.5
2024	2.0
2025	1.9
2026	1.7
2027	1.6
Thereafter	1.0
Total estimated revenue on remaining performance obligations	$	8.7

As of September 30, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $426 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 20 years. A portion of this amount is not disclosed in the table above as it is deemed variable consideration due to volume variability.

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Supplemental Cash Flow Information (Tables)

9 Months Ended

Sep. 30, 2023

Supplemental Cash Flow Elements [Abstract]

Schedule of Cash Flow, Supplemental Disclosures

	Nine Months Ended  September 30,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	724	$	642
Income taxes paid	4		2
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	8		—
Net transfers of property, plant and equipment to lease receivable	$	86	$	20

Summary of Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures

The Consolidated Statements of Cash Flows exclude changes to the Consolidated Balance Sheets that do not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures:

	Nine Months Ended  September 30,
(In millions)	2023		2022
Additions to property, plant and equipment	$	662	$	535
Increase in capital accruals	6		39
Total capital expenditures	$	668	$	574

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Description of Business and Basis of Presentation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Number of reportable segments	2

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Investments and Noncontrolling Interests (Summary of Equity Method Investment Financial Information) (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Schedule of Equity Method Investments
Equity method investments		$ 4,099	$ 4,095
L&S
Schedule of Equity Method Investments
Equity method investments		$ 1,850	1,833
L&S | Andeavor Logistics Rio Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		67.00%
Equity method investments	[1]	$ 174	177
L&S | Illinois Extension Pipeline Company, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		35.00%
Equity method investments		$ 238	236
L&S | LOOP LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		41.00%
Equity method investments		$ 301	287
L&S | MarEn Bakken Company LLC(1)
Schedule of Equity Method Investments
Equity method investment, ownership percentage		25.00%
Equity method investments	[2]	$ 453	475
L&S | Minnesota Pipe Line Company, LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		17.00%
Equity method investments		$ 174	178
L&S | Whistler Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		38.00%
Equity method investments		$ 212	211
L&S | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 298	269
L&S | Indirect Ownership Interest [Member] | Bakken Pipeline System [Member]
Schedule of Equity Method Investments
Equity method investment, ownership percentage		9.19%
G&P
Schedule of Equity Method Investments
Equity method investments		$ 2,249	2,262
G&P | Centrahoma Processing LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		40.00%
Equity method investments		$ 117	131
G&P | MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C
Schedule of Equity Method Investments
Equity method investment, ownership percentage		67.00%
Equity method investments	[1]	$ 339	335
G&P | MarkWest Torñado GP, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		60.00%
Equity method investments	[1]	$ 310	306
G&P | MarkWest Utica EMG, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		58.00%
Equity method investments	[1]	$ 684	669
G&P | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		78.00%
Equity method investments	[1]	$ 130	137
G&P | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investments	[1]	$ 116	125
G&P | Sherwood Midstream LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		50.00%
Equity method investments	[1]	$ 507	512
G&P | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 46	$ 47
G&P | Direct Ownership Interest [Member] | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		51.00%

[1] Some investments included within Other have also been deemed to be VIEs.

[2] The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL.

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Related Party Loan (Details) - Revolving Credit Facility - Related Party [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 1,500
Debt Instrument, Description of Variable Rate Basis	one-month term SOFR adjusted upward by 0.10 percent plus 1.25 percent
Line of Credit, Current	$ 0	$ 0

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Related Party Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party [Member]
Related Party Transaction [Line Items]
Sales Revenue, Goods, Related Party, Net Zero	$ 192	$ 235	$ 540	$ 809

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Related Party Expenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
General and administrative expenses	$ 102	$ 88	$ 280	$ 248
Related Party [Member]
Related Party Transaction [Line Items]
General and administrative expenses	72	60	197	173
Asset under Construction [Member] | Related Party [Member]
Related Party Transaction [Line Items]
Property, Plant and Equipment, Additions	$ 28	$ 16	$ 56	$ 54

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Related Party Assest and Liabilities (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022	Aug. 01, 2022
Related Party Transaction [Line Items]
Receivables, net		$ 833	$ 737
Other current assets		30	53
Right of use assets, net		271	283
Operating lease liabilities		48	46
Long-term deferred revenue		295	219
Related Party [Member]
Related Party Transaction [Line Items]
Receivables, net		599	610
Lease receivables		140	111
Prepaid		14	5
Other current assets		6	3
Current assets - related parties		759	729
Long-term lease receivables		811	883
Right of use assets, net		227	228
Unguaranteed residual asset		115	87	$ 6
Long-term receivables		21	27
Noncurrent assets - related parties		1,174	1,225
Accounts payable	[1]	312	262
Deferred revenue		74	80
Operating lease liabilities		1	1
Other current liabilities		387	343
Long-term operating lease liabilities		226	228
Long-term deferred revenue		117	110	$ 0
Other Liabilities, Noncurrent		343	338
Revolving Credit Facility | Related Party [Member]
Related Party Transaction [Line Items]
Line of Credit, Current		$ 0	$ 0

[1] There were no borrowings outstanding on the MPC Loan Agreement as of September 30, 2023 or December 31, 2022.

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Equity - Changes in Partners Capital, Unit Rollforward (Details)	9 Months Ended
	Sep. 30, 2023 shares
Stockholders Equity [Line Items]
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	196,428
Balance at September 30, 2023	1,001,217,044

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Repurchase Program (Details) - USD ($) $ in Millions	Sep. 30, 2023	Aug. 02, 2022
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount		$ 1,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 846

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Series B Redemption (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended						9 Months Ended
	Feb. 15, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Distributions		$ 787	$ 785	$ 808	$ 744	$ 724	$ 746
Series B Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Units, Redeemed	600,000
Dividend rate, percentage								6.875%
Preferred Stock, Redemption Price Per Share	$ 1,000
Partners' Capital Account, Distributions	$ 21
Distribution date	Feb. 15, 2023

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Equity - Cash Distributions (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended						9 Months Ended
	Nov. 13, 2023	Nov. 03, 2023	Oct. 24, 2023	Feb. 15, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023		Sep. 30, 2022
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 876			$ 810			$ 2,479		$ 2,300
Cash distributions declared per limited partner common unit					$ 0.850	$ 0.775	$ 0.775	$ 0.775	$ 0.705	$ 0.705
Series A Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 25			$ 23			71		65
Series B Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					0			10			5	[1]	31
Distribution date				Feb. 15, 2023
Common Unit-holders Public
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 851			$ 777			$ 2,403		$ 2,204
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared			$ 851
Distribution Made to Limited Partner, Declaration Date			Oct. 24, 2023
Cash distributions declared per limited partner common unit			$ 0.850
Subsequent Event | Common Unit-holders Public
Distribution Made to Limited Partner [Line Items]
Distribution date	Nov. 13, 2023
Date of record		Nov. 03, 2023

[1] The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Net Income Per Limited Partner Unit - Schedule of Distributions by Partner by Class (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022		Sep. 30, 2023		Sep. 30, 2022
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	$ 918	$ 1,428		$ 2,794		$ 3,128
Distribution Made to Limited Partner, Cash Distributions Declared		876	810		2,479		2,300
Undistributed net gain attributable to MPLX LP		$ 42	$ 618	[2]	$ 315		$ 828	[2]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1	1		1		1
Series A Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	$ 26	$ 41		$ 80		$ 89
Distribution Made to Limited Partner, Cash Distributions Declared		25	23		71		65
Undistributed net gain attributable to MPLX LP		1	18	[2]	9		24	[2]
Series B Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]		10		5		31
Distribution Made to Limited Partner, Cash Distributions Declared		0	10		5	[3]	31
Undistributed net gain attributable to MPLX LP			0	[2]	0		0	[2]
Common Unit-holders Public
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	892	1,377		2,709		3,008
Distribution Made to Limited Partner, Cash Distributions Declared		851	777		2,403		2,204
Undistributed net gain attributable to MPLX LP		$ 41	$ 600	[2]	$ 306		$ 804	[2]

[1] Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

[2] The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the three months ended September 30, 2022. See Note 14 for additional information.

[3] The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Net Income Per Limited Partner Unit - Basic and Diluted Earnings Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022		Sep. 30, 2023		Sep. 30, 2022
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 876	$ 810		$ 2,479		$ 2,300
Undistributed net gain attributable to MPLX LP		42	618	[1]	315		828	[1]
Net income attributable to MPLX LP	[2]	$ 918	$ 1,428		2,794		$ 3,128
Impact of redemption of Series B preferred units					(5)
Net Income (Loss) Available to Common Stockholders, Basic					$ 2,789
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1	1		1		1
Weighted average units outstanding:
Common - basic		1,001	1,010		1,001		1,012
Common - diluted		1,001	1,011		1,001		1,013
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.89	$ 1.36		$ 2.70		$ 2.97
Common - diluted		$ 0.89	$ 1.36		$ 2.70		$ 2.97
Series A Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 25	$ 23		$ 71		$ 65
Undistributed net gain attributable to MPLX LP		1	18	[1]	9		24	[1]
Net income attributable to MPLX LP	[2]	26	41		80		89
Series B Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		0	10		5	[3]	31
Undistributed net gain attributable to MPLX LP			0	[1]	0		0	[1]
Net income attributable to MPLX LP	[2]		10		5		31
Common Unit-holders Public
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		851	777		2,403		2,204
Undistributed net gain attributable to MPLX LP		41	600	[1]	306		804	[1]
Net income attributable to MPLX LP	[2]	$ 892	$ 1,377		2,709		$ 3,008
Impact of redemption of Series B preferred units					(5)
Net Income (Loss) Available to Common Stockholders, Basic					$ 2,704

[1] The undistributed net gain attributable to MPLX LP includes a $509 million non-cash gain on a lease reclassification for the three months ended September 30, 2022. See Note 14 for additional information.

[2] Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

[3] The nine months ended September 30, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

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Segment Information (Details)	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Number of reportable segments	2

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Segment Information - Segment Adjusted EBITDA (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022		Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,283	$ 2,321		$ 6,486	$ 6,837
Sales-type lease revenue		34	28		101	28
Income from equity method investments		159	125		438	335
Revenues		2,912	3,401		8,315	8,951
Capital Expenditure					668	574
Investments in unconsolidated affiliates					90	198
L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,136	1,042		3,237	3,046
G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,147	1,279		3,249	3,791
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA		1,596	1,471		4,646	4,321
Operating Segments | L&S
Segment Reporting Information [Line Items]
Rental income		216	210		638	593
Sales-type lease revenue		129	118		379	343
Income from equity method investments		95	72		248	183
Other Income		15	8		47	42
Revenues	[1]	1,591	1,450		4,549	4,207
Adjusted EBITDA	[2]	1,091	969		3,139	2,839
Capital Expenditure		73	80		251	238
Investments in unconsolidated affiliates		7	12		23	90
Operating Segments | G&P
Segment Reporting Information [Line Items]
Rental income		52	66		155	239
Sales-type lease revenue		34	28		101	28
Income from equity method investments		64	53		190	152
Other Income		24	525	[3]	71	534	[3]
Revenues	[1]	1,321	1,951		3,766	4,744
Adjusted EBITDA	[2]	505	502		1,507	1,482
Capital Expenditure		151	146		417	336
Investments in unconsolidated affiliates		6	30		67	108
Service [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,130	1,038		3,223	3,031
Service [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		549	537		1,620	1,528
Product [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		6	4		14	15
Product [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		598	742		1,629	2,263
Third Party [Member] | L&S
Segment Reporting Information [Line Items]
Revenues		207	175		564	468
Third Party [Member] | G&P
Segment Reporting Information [Line Items]
Revenues		$ 1,248	$ 1,885		$ 3,553	$ 4,551

[1] Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $564 million for the three and nine months ended September 30, 2023, respectively, and $175 million and $468 million for the three and nine months ended September 30, 2022, respectively. Third party revenues for the G&P segment were $1,248 million and $3,553 million for the three and nine months ended September 30, 2023, respectively, and $1,885 million and $4,551 million for the three and nine months ended September 30, 2022, respectively.

[2] See below for the reconciliation from Segment Adjusted EBITDA to Net income.

[3] The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 in the unaudited consolidated financial statements for additional information.

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Segment Information - Reconciliation to Net Income (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2023		Sep. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization	[1]	$ 301		$ 302	$ 907		$ 925
Gain on sales-type lease					0		509
Income from equity method investments		159		125	438		335
Net income		928		1,437	2,822		3,154
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA		1,596		1,471	4,646		4,321
Segment Reconciling Items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Gain on sales-type lease		0		509	0		509
Interest and Other Financial Costs		225		236	701		691
Distributions/adjustments related to equity method investments		208		166	551		450
Adjusted EBITDA attributable to noncontrolling interests		11		10	31		29
Garyville incident response costs		(63)	[2]	0	(63)	[2]	0
Other Noncash Income (Expense)	[3]	41		(26)	71		(26)
L&S
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization		130		128	399		387
L&S | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[4]	1,091		969	3,139		2,839
Income from equity method investments		95		72	248		183
G&P
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization		171		174	508		538
G&P | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[4]	505		502	1,507		1,482
Income from equity method investments		$ 64		$ 53	$ 190		$ 152

[1] Depreciation and amortization attributable to L&S was $130 million and $399 million for the three and nine months ended September 30, 2023, respectively, and $128 million and $387 million for the three and nine months ended September 30, 2022, respectively. Depreciation and amortization attributable to G&P was $171 million and $508 million for the three and nine months ended September 30, 2023, respectively, and $174 million and $538 million for the three and nine months ended September 30, 2022, respectively.

[2] In August 2023, a naphtha release and resulting fire occurred at our Garyville Tank Farm resulting in the loss of four storage tanks with a combined shell capacity of 894 thousand barrels. We incurred $63 million of incident response costs during the three and nine months ended September 30, 2023.

[3] Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

[4] See below for the reconciliation from Segment Adjusted EBITDA to Net income.

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Property, Plant and Equipment (Summary of Property, Plant and Equipment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Gross PP&E	$ 26,477		$ 26,477		$ 25,911
Accumulated Depreciation	7,857		7,857		7,063
Net PP&E	18,620		18,620		18,848
Capitalized interest	4	$ 2	11	$ 7
L&S
Property, Plant and Equipment [Line Items]
Gross PP&E	12,633		12,633		12,416
Accumulated Depreciation	3,919		3,919		3,554
Net PP&E	8,714		8,714		8,862
G&P
Property, Plant and Equipment [Line Items]
Gross PP&E	13,844		13,844		13,495
Accumulated Depreciation	3,938		3,938		3,509
Net PP&E	$ 9,906		$ 9,906		$ 9,986

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Fair Values - Recurring - Balance Sheet Location Table (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	$ 2	$ 0
Derivative Liability, Subject to Master Netting Arrangement, before Offset	60	61
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	2	0
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	0	0
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	0	0
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	0	0
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	10	10
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 50	$ 51

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Fair Values - Recurring - Significant Unobservable Inputs in Level 3 Valuation (Details)	9 Months Ended
	Sep. 30, 2023 USD ($) $ / gal
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Average Forward Price | $ / gal	0.79
Embedded Derivative Financial Instruments [Member] | Natural Gas [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Embedded Derivative Renewal Term	5 years
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs Probability of Renewal	100.00%
Minimum [Member] | Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Forward Price	0.61
Maximum [Member] | Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Forward Price	1.66

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Changes in Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (53)	$ (92)	$ (61)	$ (108)
Unrealized and realized (loss)/gain included in Net Income(1)	[1]	(10)	44	(7)	52
Settlements		3	2	8	10
Ending balance		$ (60)	$ (46)	$ (60)	$ (46)

[1] (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.

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Fair Value Measurements Gain/Loss Included in Earnings Relating to Assets Still Held at End of Period (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value Disclosures [Abstract]
The amount of total (loss)/gain for the period included in earnings attributable to the change in unrealized gain relating to liabilities still held at end of period	$ (9)	$ 42	$ (6)	$ 50

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Fair Values - Reported (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 17,922	$ 18,095
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 20,536	$ 19,905

[1] Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

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Schedule of Outstanding Derivative Positions (Details)	Sep. 30, 2023 gal
Propane | Short | Over-the-Counter
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	16,827,000

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Derivative Financial Instruments - Embedded Derivatives in Commodity Contracts (Details) - Embedded Derivative Financial Instruments [Member] $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Liability	$ (60)	$ (61)
Natural Gas [Member]
Derivative [Line Items]
Number of Renewals	1
Embedded Derivative Renewal Term	5 years

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Derivative Financial Instruments - Derivatives Balance Sheet Location (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 60	$ 61
Other Current Liabilities [Member] | Embedded Derivative Financial Instruments [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	10	10
Other Noncurrent Liabilities [Member] | Embedded Derivative Financial Instruments [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 50	$ 51

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Derivatives Financial Instruments - Derivative Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (15)	$ 44	$ (2)	$ 52
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income	Net income	Net income
Purchased product costs
Derivative [Line Items]
Realized gain (loss)	$ (3)	$ (2)	$ (8)	$ (10)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(7)	46	1	62
Derivative, Gain (Loss) on Derivative, Net	(10)	44	(7)	52
Product Sales
Derivative [Line Items]
Realized gain (loss)	3	0	3	0
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(8)	0	2	0
Derivative, Gain (Loss) on Derivative, Net	$ (5)	$ 0	$ 5	$ 0

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Debt - Summary of Outstanding Borrowings (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
MPLX Credit Agreement	$ 0	$ 0
Finance lease obligations	7	8
Debt and Lease Obligation	20,707	20,108
Unamortized debt issuance costs	(125)	(117)
Unamortized discount	(164)	(195)
Amounts due within one year	1	988
Total long-term debt due after one year	20,417	18,808
MPLX LP [Member]
Debt Instrument [Line Items]
Senior Notes	20,657	20,046
MarkWest [Member]
Debt Instrument [Line Items]
Senior Notes	12	23
ANDX LP [Member]
Debt Instrument [Line Items]
Senior Notes	$ 31	$ 31

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Credit Agreement (Detail) - USD ($) $ in Millions	Jul. 07, 2022	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term Line of Credit		$ 0	$ 0
MPLX Revolving Credit Facility due June 2027
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,000
Letter of Credit, Issuing Capacity	$ 150
Debt Instrument, Description of Variable Rate Basis	Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin.

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Senior Notes (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Mar. 13, 2023	Feb. 09, 2023
Series B Preferred Stock [Member]
Debt Instrument [Line Items]
Payments for Repurchase of Preferred Stock and Preference Stock	$ 600	$ 0
Senior Notes [Member] | Senior Notes Due March 2033 and March 2053
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 1,600
Senior Notes [Member] | Senior Note Due March 2033
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.00%
Debt Instrument, Face Amount				$ 1,100
Percent of Par				99.17%
Senior Notes [Member] | Senior Note Due March 2053
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.65%
Debt Instrument, Face Amount				$ 500
Percent of Par				99.536%
Senior Notes [Member] | Senior Notes Due July 2023
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.50%
Gain (Loss) on Extinguishment of Debt	9
Repayments of Debt	$ 1,000
Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%
Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.65%

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Revenue Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,283	$ 2,321	$ 6,486	$ 6,837
Revenue Not from Contract with Customer, Other	[1]	629	1,080	1,829	2,114
Revenues		2,912	3,401	8,315	8,951
L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,136	1,042	3,237	3,046
L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,591	1,450	4,549	4,207
G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,147	1,279	3,249	3,791
G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,321	1,951	3,766	4,744
Service [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		641	627	1,881	1,758
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		1,038	948	2,962	2,801
Service [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		97	94	272	243
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		1,033	944	2,951	2,788
Service [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,130	1,038	3,223	3,031
Service [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		544	533	1,609	1,515
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		5	4	11	13
Service [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		549	537	1,620	1,528
Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		75	83	214	324
Service, Other [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		0	0	0	0
Service, Other [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		75	83	214	324
Product [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		478	617	1,274	1,812
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		51	46	155	142
Product [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		2	2	4	5
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		4	2	10	10
Product [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		6	4	14	15
Product [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		476	615	1,270	1,807
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		47	44	145	132
Product [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 598	$ 742	$ 1,629	$ 2,263

[1] Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.

[2] Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $564 million for the three and nine months ended September 30, 2023, respectively, and $175 million and $468 million for the three and nine months ended September 30, 2022, respectively. Third party revenues for the G&P segment were $1,248 million and $3,553 million for the three and nine months ended September 30, 2023, respectively, and $1,885 million and $4,551 million for the three and nine months ended September 30, 2022, respectively.

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Revenue Contract Balances (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Aug. 01, 2022	Jul. 31, 2022	Dec. 31, 2021
Contract assets		$ 2	$ 16	$ 21			$ 25
Contract assets, additions/(deletions)		(19)	(9)
Contract with Customer, Asset, Reclassified to Receivable	[1]	0	0
Long-term contract assets		1	2	1			2
Contract with Customer, Asset Increase (Decrease), Noncurrent		0	0
Contract With Customer Non Current Asset Reclassified To Receivable [Line Items]	[1]	0	0
Long-term deferred revenue		295		219
Long-term contract liabilities		0	4	2			5
Contract Liability, Noncurrent, Period Increase (Decrease)		(2)	(1)
Contract Liability, Noncurrent, Revenue Recognized	[1]	0	0
Liability, change in timeframe, performance obligation satisfied, revenue recognized		0	0
Nonrelated Party [Member]
Deferred revenue		50	63	57			56
Deferred revenue, revenue recognized	[1]	(31)	(33)
Deferred Revenue, Additions		24	40
Long-term deferred revenue		292	162	216		$ 277	135
Long-term deferred revenue, additions/(deletions)		76	27
Long-term deferred revenue, revenue recognized	[1]	0	0
Related Party [Member]
Deferred revenue		74		80
Deferred revenue, revenue recognized	[1]	(72)	(83)
Deferred Revenue, Additions		63	79
Deferred Revenue from Contracts with Customers, Current		54	56	63			60
Long-term deferred revenue		117		110	$ 0
Long-term deferred revenue, additions/(deletions)		5	(5)
Long-term deferred revenue, revenue recognized	[1]	0	0
Deferred Revenue from Contracts with Customers, Noncurrent		$ 30	$ 26	$ 25			$ 31

[1] No significant revenue was recognized related to past performance obligations in the current periods.

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Revenue Remaining Performance Obligations (Details) $ in Millions	Sep. 30, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Contract with customer, liability	$ 426
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 8,700
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	3 months
Revenue, Remaining Performance Obligation, Amount	$ 500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 2,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 1,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 1,700
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 1,600
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years
Revenue, Remaining Performance Obligation, Amount	$ 1,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2043-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	20 years

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Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Supplemental Cash Flow Elements [Abstract]
Interest paid (net of amounts capitalized)	$ 724	$ 642
Income taxes paid	4	2
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	8	0
Property, Plant and Equipment, Transfers and Changes	$ 86	$ 20

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Supplemental Cash Flow Information - Summary of Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment	$ 662	$ 535
Increase in capital accruals	6	39
Total capital expenditures	$ 668	$ 574

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Leases, Codification Topic 842 (Details) - USD ($) $ in Millions		3 Months Ended						9 Months Ended
		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Aug. 01, 2022	Jul. 31, 2022	Dec. 31, 2021
Lessor, Lease, Description [Line Items]
Property, plant and equipment, net		$ (18,620)						$ (18,620)		$ (18,848)
Deferred revenue		295						295		219
Partners' Capital Account, Contributions		7	$ 5	$ 8	$ 55	$ 2	$ 10
Sales-type Lease, Selling Profit (Loss)								0	$ 509
Related Party [Member]
Lessor, Lease, Description [Line Items]
Sales-type Lease, Lease Receivable											$ 79
Unguaranteed residual asset		115						115		87	6
Property, plant and equipment, net											(42)
Deferred revenue		117						117		110	$ 0
Partners' Capital Account, Contributions	[1]				43
Nonrelated Party [Member]
Lessor, Lease, Description [Line Items]
Sales-type Lease, Lease Receivable												$ 914
Unguaranteed residual asset												63
Property, plant and equipment, net												(745)
Deferred revenue		$ 292			162			$ 292	$ 162	$ 216		$ 277	$ 135
Sales-type Lease, Selling Profit (Loss)	[2]				$ 509

[1] The amount recognized on commencement date was recorded as a Contribution from MPC in the Consolidated Statements of Equity given the underlying agreements are between entities under common control

[2] The amount recognized on commencement date was recorded as a gain in Other income in the Consolidated Statements of Income.

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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	9 Months Ended
	Dec. 15, 2020	Jul. 31, 2020	Sep. 30, 2023	Dec. 31, 2022
Commitments And Contingencies [Line Items]
Accrued liabilities for environmental remediation			$ 23	$ 17
Loss Contingency, Damages Sought, Value		$ 187
Loss Contingency, Damages Paid, Value	$ 4
Guarantor Obligations, Origin and Purpose			Guarantees related to indebtedness of equity method investeesWe hold a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The Army Corps has not provided a definitive date as to when a final decision would be issued.In May 2021, the D.D.C. denied a renewed request for an injunction to shut down the pipeline while the EIS is being prepared. In June 2021, the D.D.C. issued an order dismissing without prejudice the tribes’ claims against the Dakota Access Pipeline. The litigation could be reopened or new litigation challenging the EIS, once completed, could be filed. The pipeline remains operational.We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system. If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of September 30, 2023, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]			Other long-term liabilities, Other current liabilities	Other long-term liabilities, Other current liabilities
Financial Guarantee [Member] | Bakken Pipeline System [Member] | Guarantee of Indebtedness of Others [Member]
Commitments And Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 170