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 March 31, 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 1,001,168,883 common units outstanding as of April 26, 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	22
Item 3.	Quantitative and Qualitative Disclosures about Market Risk	37
Item 4.	Controls and Procedures	38
PART II – OTHER INFORMATION
Item 1.	Legal Proceedings	39
Item 1A.	Risk Factors	39
Item 6.	Exhibits	40
	Signatures	41

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.

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
Btu	One British thermal unit, an energy measurement
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  March 31,
(In millions, except per unit data)	2023		2022
Revenues and other income:
Service revenue	$	605	$	554
Service revenue - related parties	953		915
Service revenue - product related	79		123
Rental income	61		91
Rental income - related parties	202		165
Product sales	420		497
Product sales - related parties	70		45
Sales-type lease revenue	34		—
Sales-type lease revenue - related parties	125		111
Income from equity method investments	134		99
Other income (loss)	3		(17)
Other income - related parties	27		27
Total revenues and other income	2,713		2,610
Costs and expenses:
Cost of revenues (excludes items below)	308		287
Purchased product costs	406		467
Rental cost of sales	20		37
Rental cost of sales - related parties	7		15
Purchases - related parties	361		319
Depreciation and amortization	296		313
General and administrative expenses	89		78
Other taxes	30		34
Total costs and expenses	1,517		1,550
Income from operations	1,196		1,060
Related-party interest and other financial costs	—		4
Interest expense, net of amounts capitalized	224		198
Other financial costs	19		20
Income before income taxes	953		838
Provision for income taxes	1		5
Net income	952		833
Less: Net income attributable to noncontrolling interests	9		8
Net income attributable to MPLX LP	943		825
Less: Series A preferred unitholders interest in net income	23		21
Less: Series B preferred unitholders interest in net income	5		11
Limited partners' interest in net income attributable to MPLX LP	$	915	$	793
Per Unit Data (See Note 6)
Net income attributable to MPLX LP per limited partner unit:
Common - basic	$	0.91	$	0.78
Common - diluted	$	0.91	$	0.78
Weighted average limited partner units outstanding:
Common - basic	1,001		1,015
Common - diluted	1,001		1,015

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

3

MPLX LP

Consolidated Statements of Comprehensive Income (Unaudited)

	Three Months Ended  March 31,
(In millions)	2023		2022
Net income	$	952	$	833
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	956		842
Less comprehensive income attributable to:
Noncontrolling interests	9		8
Comprehensive income attributable to MPLX LP	$	947	$	834

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

4

MPLX LP

Consolidated Balance Sheets (Unaudited)

 

(In millions)	March 31, 2023		December 31, 2022
Assets
Cash and cash equivalents	$	393	$	238
Receivables, net	714		737
Current assets - related parties	701		729
Inventories	141		148
Other current assets	63		53
Total current assets	2,012		1,905
Equity method investments	4,144		4,095
Property, plant and equipment, net	18,758		18,848
Intangibles, net	673		705
Goodwill	7,645		7,645
Right of use assets, net	274		283
Noncurrent assets - related parties	1,212		1,225
Other noncurrent assets	954		959
Total assets	35,672		35,665
Liabilities
Accounts payable	139		224
Accrued liabilities	266		269
Current liabilities - related parties	327		343
Accrued property, plant and equipment	158		128
Long-term debt due within one year	1		988
Accrued interest payable	192		237
Operating lease liabilities	45		46
Other current liabilities	184		166
Total current liabilities	1,312		2,401
Long-term deferred revenue	233		219
Long-term liabilities - related parties	338		338
Long-term debt	20,393		18,808
Deferred income taxes	13		13
Long-term operating lease liabilities	221		230
Other long-term liabilities	114		142
Total liabilities	22,624		22,151
Commitments and contingencies (see Note 14)
Series A preferred units (30 million and 30 million units issued and outstanding)	968		968
Equity
Common unitholders - public (354 million and 354 million units issued and outstanding)	8,459		8,413
Common unitholders - MPC (647 million and 647 million units issued and outstanding)	3,388		3,293
Series B preferred units (0.0 million and 0.6 million units issued and outstanding)	—		611
Accumulated other comprehensive loss	(4)		(8)
Total MPLX LP partners’ capital	11,843		12,309
Noncontrolling interests	237		237
Total equity	12,080		12,546
Total liabilities, preferred units and equity	$	35,672	$	35,665

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

5

MPLX LP

Consolidated Statements of Cash Flows (Unaudited)

	Three Months Ended  March 31,
(In millions)	2023		2022
Operating activities:
Net income	$	952	$	833
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs	17		18
Depreciation and amortization	296		313
Deferred income taxes	—		4
Loss on disposal of assets	—		18
Income from equity method investments	(134)		(99)
Distributions from unconsolidated affiliates	140		120
Change in fair value of derivatives	(5)		(9)
Changes in:
Receivables	38		(87)
Inventories	(2)		(7)
Accounts payable and accrued liabilities	(130)		73
Assets/liabilities - related parties	44		(112)
Right of use assets/operating lease liabilities	(1)		(1)
Deferred revenue	3		16
All other, net	9		45
Net cash provided by operating activities	1,227		1,125
Investing activities:
Additions to property, plant and equipment	(169)		(169)
Disposal of assets	—		3
Investments in unconsolidated affiliates	(51)		(110)
Net cash used in investing activities	(220)		(276)
Financing activities:
Long-term debt borrowings	1,589		2,385
Long-term debt repayments	(1,000)		(1,201)
Related party debt borrowings	—		1,849
Related party debt repayments	—		(2,976)
Debt issuance costs	(15)		(16)
Unit repurchases	—		(100)
Redemption of Series B preferred units	(600)		—
Distributions to noncontrolling interests	(10)		(9)
Distributions to Series A preferred unitholders	(23)		(21)
Distributions to Series B preferred unitholders	(21)		(21)
Distributions to unitholders and general partner	(777)		(716)
Contributions from MPC	8		10
All other, net	(3)		(4)
Net cash used in financing activities	(852)		(820)
Net change in cash, cash equivalents and restricted cash	155		29
Cash, cash equivalents and restricted cash at beginning of period	238		13
Cash, cash equivalents and restricted cash at end of period	$	393	$	42

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, 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
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

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. References in this report to “MPLX LP,” “MPLX,” “the Partnership,” “we,” “ours,” “us,” or like terms refer to MPLX LP and its subsidiaries. References to our sponsor and customer, “MPC,” refer collectively to Marathon Petroleum Corporation and its subsidiaries, other than the Partnership. 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 months ended March 31, 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.

Certain prior period financial statement amounts have been reclassified to conform to current period presentation.

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
		March 31,	March 31,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	176	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	243		236
LOOP LLC		41%	292		287
MarEn Bakken Company LLC(1)		25%	466		475
Minnesota Pipe Line Company, LLC		17%	177		178
Whistler Pipeline LLC		38%	217		211
Other(2)	X		289		269
Total L&S			1,860		1,833
G&P
Centrahoma Processing LLC		40%	129		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	336		335
MarkWest Torñado GP, L.L.C.	X	60%	312		306
MarkWest Utica EMG, L.L.C.	X	58%	692		669
Rendezvous Gas Services, L.L.C.	X	78%	135		137
Sherwood Midstream Holdings LLC	X	51%	122		125
Sherwood Midstream LLC	X	50%	509		512
Other(2)	X		49		47
Total G&P			2,284		2,262
Total			$	4,144	$	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.

Sherwood Midstream LLC (“Sherwood Midstream”) has been deemed the primary beneficiary of Sherwood Midstream Holdings LLC (“Sherwood Midstream Holdings”) due to its controlling financial interest through its authority to manage the joint venture. As a result, Sherwood Midstream consolidates Sherwood Midstream Holdings. Therefore, MPLX also reports its portion of Sherwood Midstream Holdings’ net assets as a component of its investment in Sherwood Midstream. As of March 31, 2023, MPLX had a 24.54 percent indirect ownership interest in Sherwood Midstream Holdings through Sherwood Midstream.

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 three months ended March 31, 2023. See Note 14 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

9

fees for storage capacity; operating and management fees; as well as 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.

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 three months ended March 31, 2023.

Related Party Revenue

Related party sales to MPC primarily consist of crude oil and refined products pipeline and trucking transportation services 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 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 months ended March 31, 2023 and March 31, 2022, these sales totaled $198 million and $293 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 months ended March 31, 2023 and March 31, 2022, General and administrative expenses incurred from MPC totaled $64 million and $55 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 months ended March 31, 2023 and March 31, 2022, these charges totaled $10 million and $19 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

10

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)	March 31, 2023		December 31, 2022
Current assets - related parties
Receivables	$	559	$	610
Lease receivables	121		111
Prepaid	17		5
Other	4		3
Total	701		729
Noncurrent assets - related parties
Long-term lease receivables	865		883
Right of use assets	228		228
Unguaranteed residual asset	95		87
Long-term receivables	24		27
Total	1,212		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	239		262
Deferred revenue	87		80
Operating lease liabilities	1		1
Total	327		343
Long-term liabilities - related parties
Long-term operating lease liabilities	227		228
Long-term deferred revenue	111		110
Total	$	338	$	338

(1)    There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 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. Sales to related parties for the three months ended March 31, 2023 and March 31, 2022 were $5 million and $8 million, respectively.

5. Equity

The changes in the number of common units during the three months ended March 31, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	142,742
Balance at March 31, 2023	1,001,163,358

Unit Repurchase Program

On August 2, 2022, we announced the board authorization for the repurchase of up to an additional $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 months ended March 31, 2023. As of March 31, 2023, we had $846 million remaining under the unit repurchase authorization.

11

Redemption of the Series B Preferred Units

On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding units of 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 three months ended March 31, 2023 and March 31, 2022 are included in the Consolidated Statements of Equity within Series B preferred units.

Distributions

On April 25, 2023, MPLX declared a cash distribution for the first quarter of 2023, totaling $776 million, or $0.775 per common unit. This distribution will be paid on May 15, 2023 to common unitholders of record on May 5, 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

The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three months ended March 31, 2023 and March 31, 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  March 31,
(In millions)	2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	776	$	713
Series A preferred unit distributions	23		21
Series B preferred unit distributions(1)	5		11
Total cash distributions declared	$	804	$	745

(1) Represents the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the three months ended March 31, 2023.

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 months ended March 31, 2023 and March 31, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units and Series B preferred units and 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 months ended March 31, 2023 and March 31, 2022 were less than 1 million.

	Three Months Ended  March 31,
(In millions)	2023		2022
Net income attributable to MPLX LP	$	943	$	825
Less: Distributions declared on Series A preferred units	23		21
Distributions declared on Series B preferred units	5		11
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	776		713
Undistributed net gain attributable to MPLX LP	$	139	$	80

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	Three Months Ended March 31, 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	$	776	$	23	$	5	$	804
Undistributed net gain attributable to MPLX LP	135		4		—		139
Net income attributable to MPLX LP(1)	911		$	27	$	5	943
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	906					$	938
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.91
Diluted	$	0.91

(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 March 31, 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	$	713	$	21	$	11	$	745
Undistributed net gain attributable to MPLX LP	78		2		—		80
Net income attributable to MPLX LP(1)	$	791	$	23	$	11	$	825
Weighted average units outstanding:
Basic	1,015
Diluted	1,015
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.78
Diluted	$	0.78

(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.

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  March 31,
(In millions)	2023		2022
L&S
Service revenue	$	1,033	$	983
Rental income	212		175
Product related revenue	5		4
Sales-type lease revenue	125		111
Income from equity method investments	71		52
Other income	14		12
Total segment revenues and other income(1)	1,460		1,337
Segment Adjusted EBITDA(2)	1,026		904
Capital expenditures	68		77
Investments in unconsolidated affiliates	15		68
G&P
Service revenue	525		486
Rental income	51		81
Product related revenue	564		661
Sales-type lease revenue	34		—
Income from equity method investments	63		47
Other income (loss)	16		(2)
Total segment revenues and other income(1)	1,253		1,273
Segment Adjusted EBITDA(2)	493		489
Capital expenditures	123		95
Investments in unconsolidated affiliates	$	36	$	42

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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

The table below provides a reconciliation between Net income and Segment Adjusted EBITDA.

	Three Months Ended  March 31,
(In millions)	2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,026	$	904
G&P Segment Adjusted EBITDA	493		489
Total reportable segments	1,519		1,393
Depreciation and amortization(1)	(296)		(313)
Interest and other financial costs	(243)		(222)
Income from equity method investments	134		99
Distributions/adjustments related to equity method investments	(153)		(132)
Adjusted EBITDA attributable to noncontrolling interests	10		9
Other(2)	(19)		(1)
Net income	$	952	$	833

(1)    Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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

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8. Property, Plant and Equipment

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

	March 31, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,476	$	3,673	$	8,803	$	12,416	$	3,554	$	8,862
G&P	13,607		3,652		9,955		13,495		3,509		9,986
Total	$	26,083	$	7,325	$	18,758	$	25,911	$	7,063	$	18,848

We capitalize interest as part of the cost of major projects during the construction period. Capitalized interest totaled $3 million and $2 million for the three months ended March 31, 2023 and March 31, 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 March 31, 2023 and December 31, 2022 by fair value hierarchy level.

	March 31, 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	—		11		—		10
Other noncurrent assets / Other long-term liabilities	—		47		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	58	$	—	$	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 $0.58 to $1.55 per gallon with a weighted average of $0.77 per gallon and (2) the probability of renewal of 100 percent 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  March 31,
(In millions)	2023		2022
Beginning balance	$	(61)	$	(108)
Unrealized and realized gain included in Net Income(1)	—		4
Settlements	3		5
Ending balance	$	(58)	$	(99)
The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$	—	$	5

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

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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:

	March 31, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	19,167	$	20,517	$	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.

10. Derivatives

As of March 31, 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 (gal)	Short	33,970,000

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 March 31, 2023 and December 31, 2022, the estimated fair value of this contract was a liability of $58 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 March 31, 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  March 31,
(In millions)	2023		2022
Product sales:
Unrealized gain	$	2	$	—
Product sales derivative gain	2		—
Purchased product costs:
Realized loss	(3)		(5)
Unrealized gain	3		9
Purchased product cost derivative gain	—		4
Total derivative gain included in Net income	$	2	$	4

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11. Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	March 31, 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
Financing lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(130)		(117)
Unamortized discount	(183)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,393	$	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 three months ended March 31, 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 to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the issuance of the 2033 Senior Notes and 2053 Senior Notes discussed above, 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.

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12. Revenue

Disaggregation of Revenue

The following tables represent a disaggregation of revenue for each reportable segment for the three months ended March 31, 2023 and March 31, 2022:

	Three Months Ended March 31, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	83	$	522	$	605
Service revenue - related parties	950		3		953
Service revenue - product related	—		79		79
Product sales	2		418		420
Product sales - related parties	3		67		70
Total revenues from contracts with customers	$	1,038	$	1,089	2,127
Non-ASC 606 revenue(1)					586
Total revenues and other income					$	2,713

	Three Months Ended March 31, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	72	$	482	$	554
Service revenue - related parties	911		4		915
Service revenue - product related	—		123		123
Product sales	1		496		497
Product sales - related parties	3		42		45
Total revenues from contracts with customers	$	987	$	1,147	2,134
Non-ASC 606 revenue(1)					476
Total revenues and other income					$	2,610

(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.

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The tables below reflect the changes in ASC 606 contract balances for the three-month periods ended March 31, 2023 and March 31, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2023
Contract assets	$	21	$	(5)	$	—	$	16
Long-term contract assets	1		(1)		—		—
Deferred revenue	57		2		(14)		45
Deferred revenue - related parties	63		32		(26)		69
Long-term deferred revenue	216		15		—		231
Long-term deferred revenue - related parties	25		1		—		26
Contract liabilities	—		1		—		1
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2022
Contract assets	$	25	$	(18)	$	—	$	7
Long-term contract assets	2		—		—		2
Deferred revenue	56		11		(9)		58
Deferred revenue - related parties	60		34		(26)		68
Long-term deferred revenue	135		2		—		137
Long-term deferred revenue - related parties	31		—		—		31
Long-term contract liabilities	$	5	$	—	$	—	$	5

(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) at the end of the reporting period.

As of March 31, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $370 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 21 years. A portion of this amount is not disclosed in the table below as it is deemed variable consideration due to volume variability. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less.

(In millions)
2023	$	1,346
2024	1,680
2025	1,589
2026	1,433
2027	1,312
2028 and thereafter	708
Total revenue on remaining performance obligations(1)(2)(3)	$	8,068

(1)    All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded.

(2)    Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

(3)    Only minimum volume commitments that are deemed fixed are included in the table above. MPLX has various minimum volume commitments in processing arrangements that vary based on the actual Btu content of the gas received. These amounts are deemed variable consideration and are excluded from the table above.

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13. Supplemental Cash Flow Information

	Three Months Ended  March 31,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	270	$	213
Income taxes paid	1		—
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	9		—
Net transfers of property, plant and equipment to lease receivable	$	28	$	10

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:

	Three Months Ended  March 31,
(In millions)	2023		2022
Additions to property, plant and equipment	$	169	$	169
Increase in capital accruals	22		3
Total capital expenditures	$	191	$	172

14. 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 $17 million at both March 31, 2023 and 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 seek 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

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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 a joint venture 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. 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 EIS has been delayed and the Army Corps currently expects to release a draft EIS in 2023.

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 pipeline were temporarily shut down, 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 permit and/or return the pipeline into operation. If the vacatur of the easement permit 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 March 31, 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 March 31, 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. 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, 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;

•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 March 31, 2023 and March 31, 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)    Non-GAAP measure. See reconciliations that follow for the most directly comparable GAAP measures.

Other Highlights

•Generated $1,227 million of net cash provided by operating activities, $1,268 million of distributable cash flow attributable to MPLX, and $1,005 million of adjusted free cash flow in the first quarter of 2023.

•Returned $821 million of capital to unitholders in the three months ended March 31, 2023, in the form of distributions.

•Announced a first quarter 2023 distribution of $0.7750 per common unit.

•Issued $1.6 billion of senior notes and used the proceeds to redeem all of the $0.6 billion outstanding Series B preferred units and $1.0 billion of senior notes due July 2023.

Current Economic Environment

In 2023, data indicates a slowed increase in inflation in the U.S. and globally. We cannot predict the effect of rising interest rates, the concern of a recession, and inflation and fuel prices on demand for our products and 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. To the extent permitted by competition, regulation and our existing agreements, many of which provide for inflation-based adjustments, we have passed along a portion of our increased costs to our customers in the form of higher fees and expect to continue to do so in the future.

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.

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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.

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 March 31,
(In millions)	2023		2022		Variance
Revenues and other income:
Total revenues and other income	$	2,713	$	2,610	$	103
Costs and expenses:
Cost of revenues (excludes items below)	308		287		21
Purchased product costs	406		467		(61)
Rental cost of sales	20		37		(17)
Rental cost of sales - related parties	7		15		(8)
Purchases - related parties	361		319		42
Depreciation and amortization	296		313		(17)
General and administrative expenses	89		78		11
Other taxes	30		34		(4)
Total costs and expenses	1,517		1,550		(33)
Income from operations	1,196		1,060		136
Related-party interest and other financial costs	—		4		(4)
Interest expense, net of amounts capitalized	224		198		26
Other financial costs	19		20		(1)
Income before income taxes	953		838		115
Provision for income taxes	1		5		(4)
Net income	952		833		119
Less: Net income attributable to noncontrolling interests	9		8		1
Net income attributable to MPLX LP	943		825		118
Adjusted EBITDA attributable to MPLX LP(1)	1,519		1,393		126
DCF attributable to MPLX(1)	$	1,268	$	1,210	$	58

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

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	Three Months Ended March 31,
(In millions)	2023		2022		Variance
Reconciliation of Adjusted EBITDA attributable to MPLX LP and DCF attributable to GP and LP unitholders from Net income:
Net income	$	952	$	833	$	119
Provision for income taxes	1		5		(4)
Interest and other financial costs	243		222		21
Income from operations	1,196		1,060		136
Depreciation and amortization	296		313		(17)
Income from equity method investments	(134)		(99)		(35)
Distributions/adjustments related to equity method investments	153		132		21
Other(1)	18		(4)		22
Adjusted EBITDA	1,529		1,402		127
Adjusted EBITDA attributable to noncontrolling interests	(10)		(9)		(1)
Adjusted EBITDA attributable to MPLX LP	1,519		1,393		126
Deferred revenue impacts	12		24		(12)
Sales-type lease payments, net of income	4		5		(1)
Net interest and other financial costs(2)	(217)		(204)		(13)
Maintenance capital expenditures, net of reimbursements	(44)		(14)		(30)
Equity method investment maintenance capital expenditures paid out	(5)		(3)		(2)
Other	(1)		9		(10)
DCF attributable to MPLX LP	1,268		1,210		58
Preferred unit distributions	(28)		(32)		4
DCF attributable to GP and LP unitholders	$	1,240	$	1,178	$	62

(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.

	Three Months Ended March 31,
(In millions)	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	$	1,227	$	1,125	$	102
Changes in working capital items	48		118		(70)
All other, net	(9)		(45)		36
Loss on extinguishment of debt	9		—		9
Net interest and other financial costs(1)	217		204		13
Other adjustments to equity method investment distributions	13		12		1
Other	24		(12)		36
Adjusted EBITDA	1,529		1,402		127
Adjusted EBITDA attributable to noncontrolling interests	(10)		(9)		(1)
Adjusted EBITDA attributable to MPLX LP	1,519		1,393		126
Deferred revenue impacts	12		24		(12)
Sales-type lease payments, net of income	4		5		(1)
Net interest and other financial costs(1)	(217)		(204)		(13)
Maintenance capital expenditures, net of reimbursements	(44)		(14)		(30)
Equity method investment maintenance capital expenditures paid out	(5)		(3)		(2)
Other	(1)		9		(10)
DCF attributable to MPLX LP	1,268		1,210		58
Preferred unit distributions	(28)		(32)		4
DCF attributable to GP and LP unitholders	$	1,240	$	1,178	$	62

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

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Three months ended March 31, 2023 compared to three months ended March 31, 2022

Total revenues and other income increased $103 million in the first quarter of 2023 compared to the same period of 2022. The increase was driven by higher throughput and rate escalations across the business and a $35 million increase in income from equity method investments. The increases were partially offset by a decrease in product sales revenue as a result of lower NGL prices during the first quarter of 2023 as compared to the same period of 2022.

Cost of revenues increased $21 million and rental cost of sales (including related party) decreased $25 million in the first quarter 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 $61 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to lower prices of $157 million in the Southwest and Southern Appalachia, partially offset by higher volumes in the Southwest of $82 million and increase of $6 million due to changes in the fair value of our embedded derivative.

Purchases - related parties increased $42 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to higher related-party purchased product costs and higher transportation costs.

Depreciation and amortization decreased $17 million in the first quarter 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 first quarter of 2022.

Interest expense, net of amounts capitalized increased $26 million in the first quarter 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. These increases were partially offset by lower variable rate interest in 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 months ended March 31, 2023 and March 31, 2022.

L&S Segment

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

	Three Months Ended March 31,
(In millions)	2023		2022		Variance
Service revenue	$	1,033	$	983	$	50
Rental income	212		175		37
Product related revenue	5		4		1
Sales-type lease revenue	125		111		14
Income from equity method investments	71		52		19
Other income	14		12		2
Total segment revenues and other income	1,460		1,337		123
Cost of revenues	135		141		(6)
Purchases - related parties	244		239		5
Depreciation and amortization	129		130		(1)
General and administrative expenses	49		43		6
Other taxes	19		21		(2)
Total costs and expenses	576		574		2
Segment Adjusted EBITDA	1,026		904		122
Capital expenditures	68		77		(9)
Investments in unconsolidated affiliates(1)	$	15	$	68	$	(53)

(1)    The three months ended March 31, 2022 includes a contribution of $60 million to our Bakken Pipeline joint venture to fund our share of a debt repayment by the joint venture.

Three months ended March 31, 2023 compared to three months ended March 31, 2022

Service revenue increased $50 million in the first quarter of 2023 compared to the same period of 2022. This was primarily driven by increased pipeline and terminal throughput, higher pipeline tariff rates and $5 million from refining logistics fee escalations. These increases were partially offset by a decrease of $31 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 $37 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to an increase of $20 million from changes in the presentation of revenue between service revenue, rental income and sales-type

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lease revenue driven by modifications to agreements with MPC after the first quarter of 2022. There was also increased revenue of $9 million from refining logistics primarily due to fee escalations.

Sales-type lease revenue - related parties increased $14 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to an increase of $11 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 from fee escalations.

Income from equity methods investments increased $19 million in the first quarter of 2023 compared to the same period of 2022. This was primarily driven by increased throughput on equity method investment pipeline systems.

Cost of revenues decreased $6 million due to environmental response and remediation costs incurred in the first quarter of 2022. This decrease was partially offset by pipeline imbalance losses and increased energy costs.

L&S Operating Data

	Three Months Ended  March 31,
	2023		2022
L&S
Pipeline throughput (mbpd)
Crude oil pipelines	3,642		3,380
Product pipelines	1,988		1,956
Total pipelines	5,630		5,336
Average tariff rates ($ per barrel)(1)
Crude oil pipelines	$	0.93	$	0.93
Product pipelines	0.85		0.82
Total pipelines	$	0.90	$	0.89
Terminal throughput (mbpd)	3,091		2,941
Marine Assets (number in operation)(2)
Barges	298		296
Towboats	23		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

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

	Three Months Ended March 31,
(In millions)	2023		2022		Variance
Service revenue	$	525	$	486	$	39
Rental income	51		81		(30)
Product related revenue	564		661		(97)
Sales-type lease revenue	34		—		34
Income from equity method investments	63		47		16
Other income/(loss)	16		(2)		18
Total segment revenues and other income	1,253		1,273		(20)
Cost of revenues	200		198		2
Purchased product costs	406		467		(61)
Purchases - related parties	117		80		37
Depreciation and amortization	167		183		(16)
General and administrative expenses	40		35		5
Other taxes	11		13		(2)
Total costs and expenses	941		976		(35)
Segment Adjusted EBITDA	493		489		4
Capital expenditures	123		95		28
Investments in unconsolidated affiliates	$	36	$	42	$	(6)

Three months ended March 31, 2023 compared to three months ended March 31, 2022

Service revenue increased $39 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to higher throughput fee rates in the Marcellus and Rockies, increased revenue from minimum volume commitments, and higher volumes.

Rental income decreased $30 million and sales-type lease revenue increased $34 million in the first quarter 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.

Product related revenue decreased $97 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to lower prices across all regions of $197 million, partially offset by higher volumes in the Southwest of $100 million.

Income from equity methods investments increased $16 million in the first 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 Utica. Additionally, new capacity came online in the Southwest region in the fourth quarter of 2022 driving higher volumes over the prior period.

Other income increased $18 million in the first quarter of 2023 compared to the same period of 2022 due to a loss on disposal of assets recognized in the first quarter of 2022.

Purchased product costs decreased $61 million in the first quarter of 2023 compared to the same period of 2022. This was primarily due to lower prices of $157 million in the Southwest and Southern Appalachia, partially offset by higher volumes in the Southwest of $82 million, an increase of $6 million due to changes in the fair value of our embedded derivative.

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Purchases - related parties increased $37 million in the first quarter of 2023 compared to the same period of 2022. The increase is attributable to higher volumes and associated related-party purchased product costs in the Rockies and higher transportation costs from increased throughput in the Southwest.

Depreciation and amortization decreased $16 million in the first quarter 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 first quarter of 2022.

G&P Operating Data

        

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

	MPLX LP(1)		MPLX LP Operated(2)
	Three Months Ended  March 31,		Three Months Ended  March 31,
	2023	2022	2023	2022
G&P
Gathering Throughput (MMcf/d)
Marcellus Operations	1,363	1,314	1,363	1,314
Utica Operations	—	—	2,460	1,813
Southwest Operations	1,381	1,307	1,816	1,476
Bakken Operations	156	147	156	147
Rockies Operations	442	394	564	526
Total gathering throughput	3,342	3,162	6,359	5,276
Natural Gas Processed (MMcf/d)
Marcellus Operations	4,045	4,015	5,553	5,529
Utica Operations	—	—	494	423
Southwest Operations	1,401	1,384	1,720	1,541
Southern Appalachian Operations	230	224	230	224
Bakken Operations	154	143	154	143
Rockies Operations	454	407	454	407
Total natural gas processed	6,284	6,173	8,605	8,267
C2 + NGLs Fractionated (mbpd)
Marcellus Operations(3)	533	468	533	468
Utica Operations(3)	—	—	28	23
Southern Appalachian Operations	10	10	10	10
Bakken Operations	19	21	19	21
Rockies Operations	3	4	3	4
Total C2 + NGLs fractionated(4)	565	503	593	526

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	Three Months Ended  March 31,
	2023		2022
Pricing Information
Natural Gas NYMEX HH ($ per MMBtu)	$	2.77	$	4.57
C2 + NGL Pricing ($ per gallon)(5)	$	0.77	$	1.15

(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 184 mbpd of MPLX LP consolidated total fractionated products for the three months ended March 31, 2023 and March 31, 2022, respectively. Purity ethane makes up approximately 253 mbpd and 188 mbpd of MPLX Operated total fractionated products for the three months ended March 31, 2023 and March 31, 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 will be mitigated through the use of our fee-based transportation and storage services agreements with MPC that include minimum volume commitments.

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 $393 million at March 31, 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:

	Three Months Ended  March 31,
(In millions)	2023		2022
Net cash provided by (used in):
Operating activities	$	1,227	$	1,125
Investing activities	(220)		(276)
Financing activities	(852)		(820)
Total	$	155	$	29

Net cash provided by operating activities increased $102 million in the first quarter of 2023 compared to the first quarter of 2022, primarily due to improved results from operations and decreased working capital requirements in the first quarter of 2023 compared to the first quarter of 2022.

Net cash used in investing activities decreased $56 million in the first quarter of 2023 compared to the first quarter of 2022, due to lower contributions to equity method investments. Contributions to equity method investments for the 2022 quarter included a $60 million contribution to our Bakken Pipeline joint venture to fund our share of a scheduled debt repayment by the joint venture.

Net cash used in financing activities increased $32 million in the first quarter of 2023 compared to the first quarter of 2022. The increase in the use of cash was due to $63 million of higher distributions paid to unitholders during the first quarter of 2023 as 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. Net repayments, including the redemption of the Series B preferred units, in the first quarter of 2023 as compared to net borrowings in the first quarter of 2022 resulted in an increased use of cash of $68 million. These increases were offset by decreased spending on the unit repurchase program of $100 million in the first quarter of 2023 compared to the first quarter of 2022.

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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 months ended March 31, 2023 and March 31, 2022.

	Three Months Ended  March 31,
(In millions)	2023		2022
Net cash provided by operating activities(1)	$	1,227	$	1,125
Adjustments to reconcile net cash provided by operating activities to adjusted free cash flow
Net cash used in investing activities	(220)		(276)
Contributions from MPC	8		10
Distributions to noncontrolling interests	(10)		(9)
Adjusted free cash flow	1,005		850
Distributions paid to common and preferred unitholders	(821)		(758)
Adjusted free cash flow after distributions	$	184	$	92

(1)    The three months ended March 31, 2023 and March 31, 2022 include working capital builds of $48 million and $118 million, respectively.

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 to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the issuance of the 2033 Senior Notes and 2053 Senior Notes discussed above, 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.

Our intention is to maintain an investment-grade credit profile. As of March 31, 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. 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.

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.

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Our liquidity totaled $3.9 billion at March 31, 2023 consisting of:

	March 31, 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					393
Total liquidity					$	3,893

(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.

The MPLX Credit Agreement 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 six-month period following certain acquisitions). Consolidated EBITDA is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. Other covenants restrict us and/or certain of our subsidiaries from incurring debt, creating liens on assets and entering into transactions with affiliates. As of March 31, 2023, we were in compliance with this financial covenant with a ratio of Consolidated Total Debt to Consolidated EBITDA of 3.52 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 an additional $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 three months ended March 31, 2023. As of March 31, 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 units of 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. 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

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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 March 31, 2023.

On April 25, 2023, MPLX declared a cash distribution for the first quarter of 2023, totaling $776 million, or $0.775 per common unit. This distribution will be paid on May 15, 2023 to common unitholders of record on May 5, 2023. Although our partnership agreement requires that we distribute all of our available cash 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 months ended March 31, 2023 and March 31, 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  March 31,
(In millions, except per unit data)	2023		2022
Distribution declared:
Limited partner units - public	$	274	$	257
Limited partner units - MPC	502		456
Total LP distribution declared	776		713
Series A preferred units	23		21
Series B preferred units	5		11
Total distribution declared	$	804	$	745
Quarterly cash distributions declared per limited partner common unit	$	0.775	$	0.705

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 is $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 three months ended March 31, 2023 were primarily for gas processing plants and gathering projects in the Marcellus and Permian basins. We continuously evaluate our capital plan and make changes as conditions warrant.

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Our capital expenditures are shown in the table below:

	Three Months Ended  March 31,
(In millions)	2023		2022
Capital expenditures:
Growth capital expenditures	$	139	$	148
Growth capital reimbursements(1)	(33)		(11)
Investments in unconsolidated affiliates	51		110
Capitalized interest	(3)		(2)
Total growth capital expenditures	154		245
Maintenance capital expenditures	52		24
Maintenance capital reimbursements	(8)		(10)
Total maintenance capital expenditures	44		14
Total growth and maintenance capital expenditures	198		259
Investments in unconsolidated affiliates(2)	(51)		(110)
Growth and maintenance capital reimbursements(3)	41		21
Increase in capital accruals	(22)		(3)
Capitalized interest	3		2
Additions to property, plant and equipment(2)	$	169	$	169

(1)    Growth capital reimbursements include reimbursements from customers and our Sponsor. Prior periods have been updated to reflect these reimbursements to conform to the current period presentation.

(2)    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.

(3)    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 March 31, 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 three months ended March 31, 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.

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 14 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 March 31, 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, product pipeline, and trucking transportation services 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.

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

	Three Months Ended  March 31,
	2023		2022
Total revenues and other income	50	%	48	%
Total costs and expenses	27	%	24	%

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 significant changes to our environmental matters and compliance costs during the three months ended March 31, 2023.

Critical Accounting Estimates

As of March 31, 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.

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 March 31, 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 months ended March 31, 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, including the natural gas embedded derivative, 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 March 31, 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 March 31, 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 pre-tax operating income by $2.8 million. This analysis may differ from actual results.

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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 March 31, 2023(1)		Change in Fair Value(2)		Change in Income Before Income Taxes for the Three Months Ended March 31, 2023(3)
Outstanding debt
Fixed-rate	$	19,167	$	1,626	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 March 31, 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 three months ended March 31, 2023.

(4)    MPLX had no outstanding borrowings on the MPLX Credit Agreement as of March 31, 2023.

At March 31, 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.

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 March 31, 2023, the end of the period covered by this report.

Changes in Internal Control Over Financial Reporting

During the quarter ended March 31, 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.

As previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2022, MPLX has been negotiating a consent decree with the EPA with respect to multiple alleged violations of the National Emission Standards for Hazardous Air Pollutants by the Chapita, Coyote Wash, Island, River Bend and Wonsits Valley Compressor Stations in Utah as well as the Robinson Lake Gas Plant in North Dakota. On April 18, 2023 we entered into a consent decree with the EPA pursuant to which MPLX will pay a cash penalty of $2 million, incorporate additional remedial measures, and mitigate excess emissions associated with events covering MPLX gas plants and compressor stations located in Utah, North Dakota and Wyoming. The consent decree was lodged with the United States District Court of Utah on April 20, 2023 for court approval.

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 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	First Amendment dated as of January 1, 2023 to Amended and Restated Loan Agreement dated as of July 31, 2019 by and between MPLX and MPC Investment LLC					X
10.2	Form of 2023 MPLX Phantom Unit Award Agreement	10-K	10.45	2/23/2023	001-35714
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: May 2, 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

FIRST AMENDMENT

TO

AMENDED AND RESTATED LOAN AGREEMENT

THIS FIRST AMENDMENT TO THE AMENDED AND RESTATED LOAN AGREEMENT (“Amendment”) is effective as of January 1, 2023, by and between MPLX LP, a Delaware limited partnership (the “Borrower”), and MPC Investment LLC, a Delaware limited liability company (the “Lender”). The Borrower and the Lender may be singularly referred to as a “Party” and collectively referred to as the “Parties”.

1.Purpose. The Parties acknowledge and agree that this Amendment is made and entered into for the purpose of modifying certain terms and/or conditions of the Amended and Restated Loan Agreement entered into by the Parties on July 31, 2019 (the “Loan Agreement”). The terms and conditions set forth in this Amendment shall supersede and replace the provisions of the Agreement identified herein. All terms and conditions of the Loan Agreement not modified by this Amendment shall remain in full force and effect as set forth in the Loan Agreement. All capitalized terms set forth in this Amendment shall have the same meanings as set forth in the Loan Agreement.

2.Modification. Section 3.1 of the Loan Agreement is hereby amended and replaced in its entirety with the following:

“3.1    Interest. Interest shall accrue on the unpaid principal amount of the Loans at a rate equal to the sum of (i) the one (1) month term, Term SOFR Rate (SOFR Rate) for dollar deposits, as published by the CME Term SOFR Administrator on the first Business Day of such Interest Period adjusted upward by .10%, plus (ii) a premium of one hundred twenty-five basis points (1.25%) or such lower premium applicable to one-month SOFR Rate based borrowings under the Credit Facility. Interest shall be calculated for each Interest Period on the daily principal balance of the Loan outstanding during such Interest Period on the basis of a year of 360 days for the actual number of days elapsed. The Lender’s calculation of interest accruing on any Loan shall be presumed accurate absent manifest error. In the event that borrowings based on the SOFR Rate (or a derivative thereof) cease to be available to the Borrower under the Credit Facility, the Borrower and the Lender shall negotiate in good faith to amend this Agreement to provide for a mutually agreeable replacement interest rate.”

[Signature Page Follows]

IN WITNESS WHEREOF, each of the Parties has executed this First Amendment to the Loan Agreement as of the date first written above.

MPC INVESTMENT LLC
	/s/ Maryann T. Mannen
Name:	Maryann T. Mannen
Title:	Executive Vice President and Chief Financial Officer
MPLX LP
By: MPLX GP LLC, its General Partner
	/s/ John J. Quaid
Name:	John J. Quaid
Title:	Executive Vice President and Chief Financial Officer

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: May 2, 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: May 2, 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 March 31, 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: May 2, 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 March 31, 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: May 2, 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	3 Months Ended
	Mar. 31, 2023	Apr. 26, 2023
Cover [Abstract]
Entity Central Index Key	0001552000
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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 Common Stock, Shares Outstanding		1,001,168,883

XML

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Sales-type lease revenue		$ 34	$ 0
Sales-type lease revenue - related parties		125	111
Income from equity method investments		134	99
Total revenues and other income		2,713	2,610
Costs and Expenses, Related Party		361	319
Depreciation and amortization	[1]	296	313
General and administrative expenses		89	78
Other taxes		30	34
Total costs and expenses		1,517	1,550
Operating Income (Loss)		1,196	1,060
Interest expense, net of amounts capitalized		224	198
Other financial costs		19	20
Income before income taxes		953	838
Provision for income taxes		1	5
Net income		952	833
Less: Net income attributable to noncontrolling interests		9	8
Net income attributable to MPLX LP	[2]	943	825
Limited partners' interest in net income attributable to MPLX LP		$ 915	$ 793
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.91	$ 0.78
Common - diluted		$ 0.91	$ 0.78
Weighted average limited partner units outstanding:
Common - basic		1,001	1,015
Common - diluted		1,001	1,015
Nonrelated Party [Member]
Rental income		$ 61	$ 91
Other Income		3	(17)
Rental cost of sales		20	37
Related Party [Member]
Rental income		202	165
Other Income		27	27
Rental cost of sales		7	15
General and administrative expenses		64	55
Related-party interest and other financial costs		0	4
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		953	915
Service, Other [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		70	45
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		308	287
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		406	467
Series A Preferred Stock [Member]
Net income attributable to MPLX LP	[2]	27	23
Dividends, Preferred Stock		23	21
Series B Preferred Stock [Member]
Net income attributable to MPLX LP	[2]	5	11
Dividends, Preferred Stock		5	11
Common Stock [Member]
Net income attributable to MPLX LP	[2]	$ 911	$ 791

[1] Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

[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
	Mar. 31, 2023	Mar. 31, 2022
Net income	$ 952	$ 833
Comprehensive income	956	842
Less comprehensive income attributable to:
Noncontrolling interests	9	8
Comprehensive income attributable to MPLX LP	947	834
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
Other Comprehensive Income (Loss), Net of Tax	$ 4	$ 9

XML

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents		$ 393	$ 238
Receivables, net		714	737
Inventories		141	148
Other current assets		63	53
Total current assets		2,012	1,905
Equity method investments		4,144	4,095
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization		18,758	18,848
Intangibles, net		673	705
Goodwill		7,645	7,645
Other noncurrent assets		954	959
Total assets		35,672	35,665
Liabilities
Accounts payable		139	224
Accrued liabilities		266	269
Accrued property, plant and equipment		158	128
Long-term debt due within one year		1	988
Interest Payable, Current		192	237
Operating lease liabilities		45	46
Total current liabilities		1,312	2,401
Long-term deferred revenue		233	219
Long-term debt		20,393	18,808
Deferred income taxes		13	13
Long-term operating lease liabilities		221	230
Other long-term liabilities		114	142
Total liabilities		22,624	22,151
Commitments and contingencies (see Note 14)
Equity
Accumulated other comprehensive loss		(4)	(8)
Total MPLX LP partners’ capital		11,843	12,309
Noncontrolling interests		237	237
Total equity		12,080	12,546
Total liabilities, preferred units and equity		35,672	35,665
Related Party [Member]
Liabilities
Other current liabilities		327	343
Nonrelated Party [Member]
Assets
Right of use assets, net		274	283
Liabilities
Other current liabilities		184	166
Related Party [Member]
Assets
Receivables, net		559	610
Current assets - related parties		701	729
Other current assets		4	3
Right of use assets, net		228	228
Noncurrent assets - related parties		1,212	1,225
Liabilities
Accounts payable	[1]	239	262
Operating lease liabilities		1	1
Other current liabilities		327	343
Long-term deferred revenue		111	110
Other Liabilities, Noncurrent		338	338
Long-term operating lease liabilities		227	228
Equity
Limited Partners' Capital Account		3,388	3,293
Nonrelated Party [Member]
Liabilities
Long-term deferred revenue		231	216
Equity
Limited Partners' Capital Account		8,459	8,413
Series A Preferred Stock [Member]
Liabilities
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests		968	968
Series B Preferred Stock [Member]
Equity
Preferred Units, Preferred Partners' Capital Accounts		$ 0	$ 611

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

XML

Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2023	Dec. 31, 2022
Units Outstanding	1,001,163,358	1,001,020,616
Series B Preferred Stock [Member]
Preferred Units, Issued	0.0	600,000
Preferred Units, Outstanding	0.0	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 Stock [Member] | Nonrelated Party [Member]
Units issued	354,000,000	354,000,000
Units Outstanding	354,000,000	354,000,000
Common Stock [Member] | 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		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Operating activities:
Net income		$ 952	$ 833
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs		17	18
Depreciation and amortization	[1]	296	313
Deferred income taxes		0	4
Loss on disposal of assets		0	18
Income from equity method investments		(134)	(99)
Distributions from unconsolidated affiliates		140	120
Change in fair value of derivatives		(5)	(9)
Changes in:
Receivables		38	(87)
Inventories		(2)	(7)
Accounts payable and accrued liabilities		(130)	73
Assets/liabilities - related parties		44	(112)
Right of use assets/operating lease liabilities		(1)	(1)
Deferred revenue		3	16
All other, net		9	45
Net cash provided by operating activities		1,227	1,125
Net Cash Provided by (Used in) Investing Activities [Abstract]
Additions to property, plant and equipment		(169)	(169)
Disposal of assets		0	3
Investments in unconsolidated affiliates		(51)	(110)
Net cash used in investing activities		(220)	(276)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Long-term debt borrowings		1,589	2,385
Long-term debt - repayments		(1,000)	(1,201)
Debt issuance costs		15	16
Unit repurchases		0	(100)
Distributions to noncontrolling interests		(10)	(9)
Distributions to unitholders and general partner		(777)	(716)
Contributions from MPC		8	10
All other, net		(3)	(4)
Net cash used in financing activities		(852)	(820)
Net change in cash, cash equivalents and restricted cash		155	29
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		238	13
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance		393	42
Revolving Credit Facility
Net Cash Provided by (Used in) Financing Activities [Abstract]
Related party debt borrowings		0	1,849
Related party debt repayments		0	(2,976)
Series A Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Distributions to preferred unitholders		(23)	(21)
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)	$ (21)

[1] Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

XML

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Nonrelated Party [Member]	Related Party [Member]	Series B Preferred Stock [Member]	Series A Preferred Stock [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]
Preferred Units, Preferred Partners' Capital Accounts				$ 611
Limited Partners' Capital Account		$ 8,579	$ 2,638
Noncontrolling interests							$ 241
Accumulated other comprehensive loss						$ (17)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					$ 965
Beginning Balance at Dec. 31, 2021	$ 12,052
Net income	812	287	506	11		0	8
Stock Repurchased and Retired During Period, Value	(100)	(100)	0	0	0	0	0
Distributions	(746)	(260)	(456)	(21)	(21)	0	(9)
Contributions	10	0	10	0	0	0	0
Other	8	(1)	0	0		9	0
Ending Balance at Mar. 31, 2022	12,036
Temporary Equity, Net Income					21
Temporary Equity, Other Changes					0
Preferred Units, Preferred Partners' Capital Accounts				601
Limited Partners' Capital Account		8,505	2,698
Noncontrolling interests							240
Accumulated other comprehensive loss						(8)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					965
Preferred Units, Preferred Partners' Capital Accounts				611
Limited Partners' Capital Account		8,413	3,293
Noncontrolling interests	237						237
Accumulated other comprehensive loss	(8)					(8)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					968
Beginning Balance at Dec. 31, 2022	12,546
Net income	929	323	592	5		0	9
Redemption of Series B preferred units	(600)	(2)	(3)	(595)	0	0	0
Distributions	(808)	(275)	(502)	(21)	(23)	0	(10)
Contributions	8	0	8	0	0	0	0
Other	5	0	0	0		4	1
Ending Balance at Mar. 31, 2023	12,080
Temporary Equity, Net Income					23
Temporary Equity, Other Changes					0
Preferred Units, Preferred Partners' Capital Accounts				$ 0
Limited Partners' Capital Account		$ 8,459	$ 3,388
Noncontrolling interests	237						$ 237
Accumulated other comprehensive loss	$ (4)					$ (4)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					$ 968

XML

Description of the Business and Basis of Presentation

3 Months Ended

Mar. 31, 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. References in this report to “MPLX LP,” “MPLX,” “the Partnership,” “we,” “ours,” “us,” or like terms refer to MPLX LP and its subsidiaries. References to our sponsor and customer, “MPC,” refer collectively to Marathon Petroleum Corporation and its subsidiaries, other than the Partnership. 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 months ended March 31, 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.

Certain prior period financial statement amounts have been reclassified to conform to current period presentation.

XML

Accounting Standards

3 Months Ended

Mar. 31, 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.

XML

Investments and Noncontrolling Interest

3 Months Ended

Mar. 31, 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
		March 31,	March 31,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	176	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	243		236
LOOP LLC		41%	292		287
MarEn Bakken Company LLC(1)		25%	466		475
Minnesota Pipe Line Company, LLC		17%	177		178
Whistler Pipeline LLC		38%	217		211
Other(2)	X		289		269
Total L&S			1,860		1,833
G&P
Centrahoma Processing LLC		40%	129		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	336		335
MarkWest Torñado GP, L.L.C.	X	60%	312		306
MarkWest Utica EMG, L.L.C.	X	58%	692		669
Rendezvous Gas Services, L.L.C.	X	78%	135		137
Sherwood Midstream Holdings LLC	X	51%	122		125
Sherwood Midstream LLC	X	50%	509		512
Other(2)	X		49		47
Total G&P			2,284		2,262
Total			$	4,144	$	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.

Sherwood Midstream LLC (“Sherwood Midstream”) has been deemed the primary beneficiary of Sherwood Midstream Holdings LLC (“Sherwood Midstream Holdings”) due to its controlling financial interest through its authority to manage the joint venture. As a result, Sherwood Midstream consolidates Sherwood Midstream Holdings. Therefore, MPLX also reports its portion of Sherwood Midstream Holdings’ net assets as a component of its investment in Sherwood Midstream. As of March 31, 2023, MPLX had a 24.54 percent indirect ownership interest in Sherwood Midstream Holdings through Sherwood Midstream.

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 three months ended March 31, 2023. See Note 14 for information on our Guarantees related to indebtedness of equity method investees.

XML

Related Party Agreements and Transactions

3 Months Ended

Mar. 31, 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; as well as 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.

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 three months ended March 31, 2023.

Related Party Revenue

Related party sales to MPC primarily consist of crude oil and refined products pipeline and trucking transportation services 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 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 months ended March 31, 2023 and March 31, 2022, these sales totaled $198 million and $293 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 months ended March 31, 2023 and March 31, 2022, General and administrative expenses incurred from MPC totaled $64 million and $55 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 months ended March 31, 2023 and March 31, 2022, these charges totaled $10 million and $19 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)	March 31, 2023		December 31, 2022
Current assets - related parties
Receivables	$	559	$	610
Lease receivables	121		111
Prepaid	17		5
Other	4		3
Total	701		729
Noncurrent assets - related parties
Long-term lease receivables	865		883
Right of use assets	228		228
Unguaranteed residual asset	95		87
Long-term receivables	24		27
Total	1,212		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	239		262
Deferred revenue	87		80
Operating lease liabilities	1		1
Total	327		343
Long-term liabilities - related parties
Long-term operating lease liabilities	227		228
Long-term deferred revenue	111		110
Total	$	338	$	338

(1)    There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 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. Sales to related parties for the three months ended March 31, 2023 and March 31, 2022 were $5 million and $8 million, respectively.

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Equity

3 Months Ended

Mar. 31, 2023

Equity [Abstract]

Equity

Equity

The changes in the number of common units during the three months ended March 31, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	142,742
Balance at March 31, 2023	1,001,163,358

Unit Repurchase Program

On August 2, 2022, we announced the board authorization for the repurchase of up to an additional $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 months ended March 31, 2023. As of March 31, 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 units of 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 three months ended March 31, 2023 and March 31, 2022 are included in the Consolidated Statements of Equity within Series B preferred units.

Distributions

On April 25, 2023, MPLX declared a cash distribution for the first quarter of 2023, totaling $776 million, or $0.775 per common unit. This distribution will be paid on May 15, 2023 to common unitholders of record on May 5, 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

The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three months ended March 31, 2023 and March 31, 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  March 31,
(In millions)	2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	776	$	713
Series A preferred unit distributions	23		21
Series B preferred unit distributions(1)	5		11
Total cash distributions declared	$	804	$	745

(1) Represents the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the three months ended March 31, 2023.

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Net Income Per Limited Partner Unit

3 Months Ended

Mar. 31, 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 months ended March 31, 2023 and March 31, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units and Series B preferred units and 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 months ended March 31, 2023 and March 31, 2022 were less than 1 million.

	Three Months Ended  March 31,
(In millions)	2023		2022
Net income attributable to MPLX LP	$	943	$	825
Less: Distributions declared on Series A preferred units	23		21
Distributions declared on Series B preferred units	5		11
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	776		713
Undistributed net gain attributable to MPLX LP	$	139	$	80

	Three Months Ended March 31, 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	$	776	$	23	$	5	$	804
Undistributed net gain attributable to MPLX LP	135		4		—		139
Net income attributable to MPLX LP(1)	911		$	27	$	5	943
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	906					$	938
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.91
Diluted	$	0.91

(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 March 31, 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	$	713	$	21	$	11	$	745
Undistributed net gain attributable to MPLX LP	78		2		—		80
Net income attributable to MPLX LP(1)	$	791	$	23	$	11	$	825
Weighted average units outstanding:
Basic	1,015
Diluted	1,015
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.78
Diluted	$	0.78

(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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Segment Information

3 Months Ended

Mar. 31, 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  March 31,
(In millions)	2023		2022
L&S
Service revenue	$	1,033	$	983
Rental income	212		175
Product related revenue	5		4
Sales-type lease revenue	125		111
Income from equity method investments	71		52
Other income	14		12
Total segment revenues and other income(1)	1,460		1,337
Segment Adjusted EBITDA(2)	1,026		904
Capital expenditures	68		77
Investments in unconsolidated affiliates	15		68
G&P
Service revenue	525		486
Rental income	51		81
Product related revenue	564		661
Sales-type lease revenue	34		—
Income from equity method investments	63		47
Other income (loss)	16		(2)
Total segment revenues and other income(1)	1,253		1,273
Segment Adjusted EBITDA(2)	493		489
Capital expenditures	123		95
Investments in unconsolidated affiliates	$	36	$	42

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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

The table below provides a reconciliation between Net income and Segment Adjusted EBITDA.

	Three Months Ended  March 31,
(In millions)	2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,026	$	904
G&P Segment Adjusted EBITDA	493		489
Total reportable segments	1,519		1,393
Depreciation and amortization(1)	(296)		(313)
Interest and other financial costs	(243)		(222)
Income from equity method investments	134		99
Distributions/adjustments related to equity method investments	(153)		(132)
Adjusted EBITDA attributable to noncontrolling interests	10		9
Other(2)	(19)		(1)
Net income	$	952	$	833

(1)    Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

(2)    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

3 Months Ended

Mar. 31, 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:

	March 31, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,476	$	3,673	$	8,803	$	12,416	$	3,554	$	8,862
G&P	13,607		3,652		9,955		13,495		3,509		9,986
Total	$	26,083	$	7,325	$	18,758	$	25,911	$	7,063	$	18,848

We capitalize interest as part of the cost of major projects during the construction period. Capitalized interest totaled $3 million and $2 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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Fair Value Measurements

3 Months Ended

Mar. 31, 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 March 31, 2023 and December 31, 2022 by fair value hierarchy level.

	March 31, 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	—		11		—		10
Other noncurrent assets / Other long-term liabilities	—		47		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	58	$	—	$	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 $0.58 to $1.55 per gallon with a weighted average of $0.77 per gallon and (2) the probability of renewal of 100 percent 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  March 31,
(In millions)	2023		2022
Beginning balance	$	(61)	$	(108)
Unrealized and realized gain included in Net Income(1)	—		4
Settlements	3		5
Ending balance	$	(58)	$	(99)
The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$	—	$	5

(1)     Gain/(loss) 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:

	March 31, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	19,167	$	20,517	$	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 $0.58 to $1.55 per gallon with a weighted average of $0.77 per gallon and (2) the probability of renewal of 100 percent 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

3 Months Ended

Mar. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Disclosure

Derivatives

As of March 31, 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 (gal)	Short	33,970,000

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 March 31, 2023 and December 31, 2022, the estimated fair value of this contract was a liability of $58 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 March 31, 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  March 31,
(In millions)	2023		2022
Product sales:
Unrealized gain	$	2	$	—
Product sales derivative gain	2		—
Purchased product costs:
Realized loss	(3)		(5)
Unrealized gain	3		9
Purchased product cost derivative gain	—		4
Total derivative gain included in Net income	$	2	$	4

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Debt

3 Months Ended

Mar. 31, 2023

Debt Disclosure [Abstract]

Debt

Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	March 31, 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
Financing lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(130)		(117)
Unamortized discount	(183)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,393	$	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 three months ended March 31, 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 to redeem all of the outstanding Series B preferred units. On March 13, 2023, MPLX used the remaining proceeds from the issuance of the 2033 Senior Notes and 2053 Senior Notes discussed above, 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

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Revenue

3 Months Ended

Mar. 31, 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 months ended March 31, 2023 and March 31, 2022:

	Three Months Ended March 31, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	83	$	522	$	605
Service revenue - related parties	950		3		953
Service revenue - product related	—		79		79
Product sales	2		418		420
Product sales - related parties	3		67		70
Total revenues from contracts with customers	$	1,038	$	1,089	2,127
Non-ASC 606 revenue(1)					586
Total revenues and other income					$	2,713

	Three Months Ended March 31, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	72	$	482	$	554
Service revenue - related parties	911		4		915
Service revenue - product related	—		123		123
Product sales	1		496		497
Product sales - related parties	3		42		45
Total revenues from contracts with customers	$	987	$	1,147	2,134
Non-ASC 606 revenue(1)					476
Total revenues and other income					$	2,610

(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 three-month periods ended March 31, 2023 and March 31, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2023
Contract assets	$	21	$	(5)	$	—	$	16
Long-term contract assets	1		(1)		—		—
Deferred revenue	57		2		(14)		45
Deferred revenue - related parties	63		32		(26)		69
Long-term deferred revenue	216		15		—		231
Long-term deferred revenue - related parties	25		1		—		26
Contract liabilities	—		1		—		1
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2022
Contract assets	$	25	$	(18)	$	—	$	7
Long-term contract assets	2		—		—		2
Deferred revenue	56		11		(9)		58
Deferred revenue - related parties	60		34		(26)		68
Long-term deferred revenue	135		2		—		137
Long-term deferred revenue - related parties	31		—		—		31
Long-term contract liabilities	$	5	$	—	$	—	$	5

(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) at the end of the reporting period.

As of March 31, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $370 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 21 years. A portion of this amount is not disclosed in the table below as it is deemed variable consideration due to volume variability. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less.

(In millions)
2023	$	1,346
2024	1,680
2025	1,589
2026	1,433
2027	1,312
2028 and thereafter	708
Total revenue on remaining performance obligations(1)(2)(3)	$	8,068

(1)    All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded.

(2)    Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

(3)    Only minimum volume commitments that are deemed fixed are included in the table above. MPLX has various minimum volume commitments in processing arrangements that vary based on the actual Btu content of the gas received. These amounts are deemed variable consideration and are excluded from the table above.

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Supplemental Cash Flow Information

3 Months Ended

Mar. 31, 2023

Supplemental Cash Flow Elements [Abstract]

Supplemental Cash Flow Information

Supplemental Cash Flow Information

	Three Months Ended  March 31,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	270	$	213
Income taxes paid	1		—
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	9		—
Net transfers of property, plant and equipment to lease receivable	$	28	$	10

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:

	Three Months Ended  March 31,
(In millions)	2023		2022
Additions to property, plant and equipment	$	169	$	169
Increase in capital accruals	22		3
Total capital expenditures	$	191	$	172

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Commitments and Contingencies

3 Months Ended

Mar. 31, 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 $17 million at both March 31, 2023 and 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 seek 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 a joint venture 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. 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 EIS has been delayed and the Army Corps currently expects to release a draft EIS in 2023.

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 pipeline were temporarily shut down, 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 permit and/or return the pipeline into operation. If the vacatur of the easement permit 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 March 31, 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 March 31, 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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Description of the Business and Basis of Presentation Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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)	3 Months Ended
	Mar. 31, 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)

3 Months Ended

Mar. 31, 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
		March 31,	March 31,		December 31,
(In millions, except ownership percentages)	VIE	2023	2023		2022
L&S
Andeavor Logistics Rio Pipeline LLC	X	67%	$	176	$	177
Illinois Extension Pipeline Company, L.L.C.		35%	243		236
LOOP LLC		41%	292		287
MarEn Bakken Company LLC(1)		25%	466		475
Minnesota Pipe Line Company, LLC		17%	177		178
Whistler Pipeline LLC		38%	217		211
Other(2)	X		289		269
Total L&S			1,860		1,833
G&P
Centrahoma Processing LLC		40%	129		131
MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C	X	67%	336		335
MarkWest Torñado GP, L.L.C.	X	60%	312		306
MarkWest Utica EMG, L.L.C.	X	58%	692		669
Rendezvous Gas Services, L.L.C.	X	78%	135		137
Sherwood Midstream Holdings LLC	X	51%	122		125
Sherwood Midstream LLC	X	50%	509		512
Other(2)	X		49		47
Total G&P			2,284		2,262
Total			$	4,144	$	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)

3 Months Ended

Mar. 31, 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)	March 31, 2023		December 31, 2022
Current assets - related parties
Receivables	$	559	$	610
Lease receivables	121		111
Prepaid	17		5
Other	4		3
Total	701		729
Noncurrent assets - related parties
Long-term lease receivables	865		883
Right of use assets	228		228
Unguaranteed residual asset	95		87
Long-term receivables	24		27
Total	1,212		1,225
Current liabilities - related parties
MPC loan agreement and other payables(1)	239		262
Deferred revenue	87		80
Operating lease liabilities	1		1
Total	327		343
Long-term liabilities - related parties
Long-term operating lease liabilities	227		228
Long-term deferred revenue	111		110
Total	$	338	$	338

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

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Equity (Tables)

3 Months Ended

Mar. 31, 2023

Equity [Abstract]

Schedule of Stockholders Equity

The changes in the number of common units during the three months ended March 31, 2023 are summarized below:

(In units)	Common Units
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	142,742
Balance at March 31, 2023	1,001,163,358

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 months ended March 31, 2023 and March 31, 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  March 31,
(In millions)	2023		2022
Common and preferred unit distributions:
Common unitholders, includes common units of general partner	$	776	$	713
Series A preferred unit distributions	23		21
Series B preferred unit distributions(1)	5		11
Total cash distributions declared	$	804	$	745

(1) Represents the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the three months ended March 31, 2023.

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Net Income Per Limited Partner Unit (Tables)

3 Months Ended

Mar. 31, 2023

Earnings Per Share [Abstract]

Schedule of Distributions By Partner By Class

During the three months ended March 31, 2023 and March 31, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units and Series B preferred units and 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 months ended March 31, 2023 and March 31, 2022 were less than 1 million.

	Three Months Ended  March 31,
(In millions)	2023		2022
Net income attributable to MPLX LP	$	943	$	825
Less: Distributions declared on Series A preferred units	23		21
Distributions declared on Series B preferred units	5		11
Limited partners’ distributions declared on MPLX common units (including common units of general partner)	776		713
Undistributed net gain attributable to MPLX LP	$	139	$	80

Schedule of Net Income Per Unit, Basic and Diluted

	Three Months Ended March 31, 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	$	776	$	23	$	5	$	804
Undistributed net gain attributable to MPLX LP	135		4		—		139
Net income attributable to MPLX LP(1)	911		$	27	$	5	943
Impact of redemption of Series B preferred units	(5)						(5)
Income available to common unitholders	$	906					$	938
Weighted average units outstanding:
Basic	1,001
Diluted	1,001
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.91
Diluted	$	0.91

(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 March 31, 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	$	713	$	21	$	11	$	745
Undistributed net gain attributable to MPLX LP	78		2		—		80
Net income attributable to MPLX LP(1)	$	791	$	23	$	11	$	825
Weighted average units outstanding:
Basic	1,015
Diluted	1,015
Net income attributable to MPLX LP per limited partner unit:
Basic	$	0.78
Diluted	$	0.78

(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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Segment Information (Tables)

3 Months Ended

Mar. 31, 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  March 31,
(In millions)	2023		2022
L&S
Service revenue	$	1,033	$	983
Rental income	212		175
Product related revenue	5		4
Sales-type lease revenue	125		111
Income from equity method investments	71		52
Other income	14		12
Total segment revenues and other income(1)	1,460		1,337
Segment Adjusted EBITDA(2)	1,026		904
Capital expenditures	68		77
Investments in unconsolidated affiliates	15		68
G&P
Service revenue	525		486
Rental income	51		81
Product related revenue	564		661
Sales-type lease revenue	34		—
Income from equity method investments	63		47
Other income (loss)	16		(2)
Total segment revenues and other income(1)	1,253		1,273
Segment Adjusted EBITDA(2)	493		489
Capital expenditures	123		95
Investments in unconsolidated affiliates	$	36	$	42

(1)    Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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

Reconciliation of Other Significant Reconciling Items from Segments to Consolidated

The table below provides a reconciliation between Net income and Segment Adjusted EBITDA.

	Three Months Ended  March 31,
(In millions)	2023		2022
Reconciliation to Net income:
L&S Segment Adjusted EBITDA	$	1,026	$	904
G&P Segment Adjusted EBITDA	493		489
Total reportable segments	1,519		1,393
Depreciation and amortization(1)	(296)		(313)
Interest and other financial costs	(243)		(222)
Income from equity method investments	134		99
Distributions/adjustments related to equity method investments	(153)		(132)
Adjusted EBITDA attributable to noncontrolling interests	10		9
Other(2)	(19)		(1)
Net income	$	952	$	833

(1)    Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

(2)    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)

3 Months Ended

Mar. 31, 2023

Property, Plant and Equipment [Abstract]

Summary of Property, Plant and Equipment

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

	March 31, 2023						December 31, 2022
(In millions)	Gross PP&E		Accumulated Depreciation		Net PP&E		Gross PP&E		Accumulated Depreciation		Net PP&E
L&S	$	12,476	$	3,673	$	8,803	$	12,416	$	3,554	$	8,862
G&P	13,607		3,652		9,955		13,495		3,509		9,986
Total	$	26,083	$	7,325	$	18,758	$	25,911	$	7,063	$	18,848

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Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2023 and December 31, 2022 by fair value hierarchy level.

	March 31, 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	—		11		—		10
Other noncurrent assets / Other long-term liabilities	—		47		—		51
Total carrying value in Consolidated Balance Sheets	$	2	$	58	$	—	$	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  March 31,
(In millions)	2023		2022
Beginning balance	$	(61)	$	(108)
Unrealized and realized gain included in Net Income(1)	—		4
Settlements	3		5
Ending balance	$	(58)	$	(99)
The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$	—	$	5

(1)     Gain/(loss) 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:

	March 31, 2023				December 31, 2022
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
Outstanding debt(1)	$	19,167	$	20,517	$	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)

3 Months Ended

Mar. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions

As of March 31, 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 (gal)	Short	33,970,000

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  March 31,
(In millions)	2023		2022
Product sales:
Unrealized gain	$	2	$	—
Product sales derivative gain	2		—
Purchased product costs:
Realized loss	(3)		(5)
Unrealized gain	3		9
Purchased product cost derivative gain	—		4
Total derivative gain included in Net income	$	2	$	4

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Debt (Tables)

3 Months Ended

Mar. 31, 2023

Debt Disclosure [Abstract]

Schedule of Debt

MPLX’s outstanding borrowings consist of the following:

(In millions)	March 31, 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
Financing lease obligations	7		8
Total	20,707		20,108
Unamortized debt issuance costs	(130)		(117)
Unamortized discount	(183)		(195)
Amounts due within one year	(1)		(988)
Total long-term debt due after one year	$	20,393	$	18,808

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Revenue (Tables)

3 Months Ended

Mar. 31, 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 months ended March 31, 2023 and March 31, 2022:

	Three Months Ended March 31, 2023
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	83	$	522	$	605
Service revenue - related parties	950		3		953
Service revenue - product related	—		79		79
Product sales	2		418		420
Product sales - related parties	3		67		70
Total revenues from contracts with customers	$	1,038	$	1,089	2,127
Non-ASC 606 revenue(1)					586
Total revenues and other income					$	2,713

	Three Months Ended March 31, 2022
(In millions)	L&S		G&P		Total
Revenues and other income:
Service revenue	$	72	$	482	$	554
Service revenue - related parties	911		4		915
Service revenue - product related	—		123		123
Product sales	1		496		497
Product sales - related parties	3		42		45
Total revenues from contracts with customers	$	987	$	1,147	2,134
Non-ASC 606 revenue(1)					476
Total revenues and other income					$	2,610

(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 three-month periods ended March 31, 2023 and March 31, 2022:

(In millions)	Balance at December 31, 2022		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2023
Contract assets	$	21	$	(5)	$	—	$	16
Long-term contract assets	1		(1)		—		—
Deferred revenue	57		2		(14)		45
Deferred revenue - related parties	63		32		(26)		69
Long-term deferred revenue	216		15		—		231
Long-term deferred revenue - related parties	25		1		—		26
Contract liabilities	—		1		—		1
Long-term contract liabilities	$	2	$	(2)	$	—	$	—

(In millions)	Balance at December 31, 2021		Additions/ (Deletions)		Revenue Recognized(1)		Balance at March 31, 2022
Contract assets	$	25	$	(18)	$	—	$	7
Long-term contract assets	2		—		—		2
Deferred revenue	56		11		(9)		58
Deferred revenue - related parties	60		34		(26)		68
Long-term deferred revenue	135		2		—		137
Long-term deferred revenue - related parties	31		—		—		31
Long-term contract liabilities	$	5	$	—	$	—	$	5

(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) at the end of the reporting period.

As of March 31, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $370 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 21 years. A portion of this amount is not disclosed in the table below as it is deemed variable consideration due to volume variability. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less.

(In millions)
2023	$	1,346
2024	1,680
2025	1,589
2026	1,433
2027	1,312
2028 and thereafter	708
Total revenue on remaining performance obligations(1)(2)(3)	$	8,068

(1)    All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded.

(2)    Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

(3)    Only minimum volume commitments that are deemed fixed are included in the table above. MPLX has various minimum volume commitments in processing arrangements that vary based on the actual Btu content of the gas received. These amounts are deemed variable consideration and are excluded from the table above.

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Supplemental Cash Flow Information (Tables)

3 Months Ended

Mar. 31, 2023

Supplemental Cash Flow Elements [Abstract]

Schedule of Cash Flow, Supplemental Disclosures

	Three Months Ended  March 31,
(In millions)	2023		2022
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$	270	$	213
Income taxes paid	1		—
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	9		—
Net transfers of property, plant and equipment to lease receivable	$	28	$	10

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:

	Three Months Ended  March 31,
(In millions)	2023		2022
Additions to property, plant and equipment	$	169	$	169
Increase in capital accruals	22		3
Total capital expenditures	$	191	$	172

XML

Description of Business and Basis of Presentation - Additional Information (Detail)	3 Months Ended
	Mar. 31, 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		Mar. 31, 2023	Dec. 31, 2022
Schedule of Equity Method Investments
Equity method investments		$ 4,144	$ 4,095
Indirect Ownership Interest [Member] | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		24.54%
L&S
Schedule of Equity Method Investments
Equity method investments		$ 1,860	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]	$ 176	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		$ 243	236
L&S | LOOP LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		41.00%
Equity method investments		$ 292	287
L&S | MarEn Bakken Company LLC(1)
Schedule of Equity Method Investments
Equity method investment, ownership percentage		25.00%
Equity method investments	[2]	$ 466	475
L&S | Minnesota Pipe Line Company, LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		17.00%
Equity method investments		$ 177	178
L&S | Whistler Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		38.00%
Equity method investments		$ 217	211
L&S | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 289	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		$ 2,284	2,262
G&P | Centrahoma Processing LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		40.00%
Equity method investments		$ 129	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]	$ 336	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]	$ 312	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]	$ 692	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]	$ 135	137
G&P | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investments	[1]	$ 122	125
G&P | Sherwood Midstream LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		50.00%
Equity method investments	[1]	$ 509	512
G&P | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 49	$ 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	3 Months Ended
	Mar. 31, 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
	Mar. 31, 2023	Mar. 31, 2022
Related Party [Member]
Related Party Transaction [Line Items]
Sales Revenue, Goods, Related Party, Net Zero	$ 198	$ 293

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Related Party Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Related Party Transaction [Line Items]
General and administrative expenses	$ 89	$ 78
Related Party [Member]
Related Party Transaction [Line Items]
General and administrative expenses	64	55
Asset under Construction [Member] | Related Party [Member]
Related Party Transaction [Line Items]
Property, Plant and Equipment, Additions	$ 10	$ 19

XML

Related Party Assest and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Receivables, net		$ 714	$ 737
Other current assets		63	53
Accounts payable		139	224
Operating lease liabilities		45	46
Long-term operating lease liabilities		221	230
Long-term deferred revenue		233	219
Related Party [Member]
Related Party Transaction [Line Items]
Receivables, net		559	610
Lease receivables		121	111
Prepaid		17	5
Other current assets		4	3
Current assets - related parties		701	729
Long-term lease receivables		865	883
Right of use assets, net		228	228
Unguaranteed residual asset		95	87
Long-term receivables		24	27
Noncurrent assets - related parties		1,212	1,225
Accounts payable	[1]	239	262
Deferred revenue		87	80
Operating lease liabilities		1	1
Other current liabilities		327	343
Long-term operating lease liabilities		227	228
Long-term deferred revenue		111	110
Other Liabilities, Noncurrent		338	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 March 31, 2023 or December 31, 2022.

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Other Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Related Party Transaction [Line Items]
Revenues	$ 2,713	$ 2,610
Asset and Inventory transfers | Related Party [Member]
Related Party Transaction [Line Items]
Revenues	$ 5	$ 8

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Equity - Changes in Partners Capital, Unit Rollforward (Details)	3 Months Ended
	Mar. 31, 2023 shares
Stockholders Equity [Line Items]
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	142,742
Balance at March 31, 2023	1,001,163,358

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Repurchase Program (Details) - USD ($) $ in Millions	Mar. 31, 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
	Feb. 15, 2023	Mar. 31, 2023	Mar. 31, 2022
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Distributions		$ 808	$ 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
	May 15, 2023	May 05, 2023	Apr. 25, 2023	Feb. 15, 2023	Mar. 31, 2023	Mar. 31, 2022
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 804	$ 745
Cash distributions declared per limited partner common unit					$ 0.775	$ 0.705
Series A Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 23	$ 21
Series B Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					5	11
Distribution date				Feb. 15, 2023
Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 776	$ 713
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared			$ 776
Distribution Made to Limited Partner, Declaration Date			Apr. 25, 2023
Cash distributions declared per limited partner common unit			$ 0.775
Date of record		May 05, 2023
Subsequent Event | Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution date	May 15, 2023

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Net Income Per Limited Partner Unit - Schedule of Distributions by Partner by Class (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	$ 943	$ 825
Distribution Made to Limited Partner, Cash Distributions Declared		804	745
Undistributed net gain attributable to MPLX LP		139	80
Series A Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	27	23
Distribution Made to Limited Partner, Cash Distributions Declared		23	21
Undistributed net gain attributable to MPLX LP		4	2
Series B Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	5	11
Distribution Made to Limited Partner, Cash Distributions Declared		5	11
Undistributed net gain attributable to MPLX LP		0	0
Common Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	911	791
Distribution Made to Limited Partner, Cash Distributions Declared		776	713
Undistributed net gain attributable to MPLX LP		$ 135	$ 78

[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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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
		Mar. 31, 2023	Mar. 31, 2022
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 804	$ 745
Undistributed net gain attributable to MPLX LP		139	80
Net income attributable to MPLX LP	[1]	943	$ 825
Impact of redemption of Series B preferred units		(5)
Net Income (Loss) Available to Common Stockholders, Basic		$ 938
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1	1
Weighted average units outstanding:
Common - basic		1,001	1,015
Common - diluted		1,001	1,015
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.91	$ 0.78
Common - diluted		$ 0.91	$ 0.78
Series A Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 23	$ 21
Undistributed net gain attributable to MPLX LP		4	2
Net income attributable to MPLX LP	[1]	27	23
Series B Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		5	11
Undistributed net gain attributable to MPLX LP		0	0
Net income attributable to MPLX LP	[1]	5	11
Common Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		776	713
Undistributed net gain attributable to MPLX LP		135	78
Net income attributable to MPLX LP	[1]	911	$ 791
Impact of redemption of Series B preferred units		(5)
Net Income (Loss) Available to Common Stockholders, Basic		$ 906

[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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Segment Information (Details)	3 Months Ended
	Mar. 31, 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
		Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Sales-type lease revenue - related parties		$ 125	$ 111
Sales-type lease revenue		34	0
Income from equity method investments		134	99
Revenues		2,713	2,610
Capital Expenditure		191	172
Investments in unconsolidated affiliates		51	110
L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,038	987
G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,089	1,147
Operating Segments
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2,127	2,134
Adjusted EBITDA		1,519	1,393
Operating Segments | L&S
Segment Reporting Information [Line Items]
Rental income		212	175
Sales-type lease revenue		125	111
Income from equity method investments		71	52
Other income		14	12
Revenues	[1]	1,460	1,337
Adjusted EBITDA	[2]	1,026	904
Capital Expenditure		68	77
Investments in unconsolidated affiliates		15	68
Operating Segments | G&P
Segment Reporting Information [Line Items]
Rental income		51	81
Sales-type lease revenue		34	0
Income from equity method investments		63	47
Other income		16	(2)
Revenues	[1]	1,253	1,273
Adjusted EBITDA	[2]	493	489
Capital Expenditure		123	95
Investments in unconsolidated affiliates		36	42
Service [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Service [Member] | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		83	72
Service [Member] | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		522	482
Service [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,033	983
Service [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		525	486
Product [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Product [Member] | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2	1
Product [Member] | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		418	496
Product [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5	4
Product [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		564	661
Third Party [Member] | L&S
Segment Reporting Information [Line Items]
Revenues		170	135
Third Party [Member] | G&P
Segment Reporting Information [Line Items]
Revenues		$ 1,166	$ 1,212

[1] Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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

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Segment Information - Reconciliation to Net Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)	[1]	$ (296)	$ (313)
Income from equity method investments		134	99
Proceeds from Equity Method Investment, Distribution		(140)	(120)
Net income		952	833
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA		1,519	1,393
Segment Reconciling Items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Interest and Other Financial Costs		(243)	(222)
Proceeds from Equity Method Investment, Distribution		(153)	(132)
Adjusted EBITDA attributable to noncontrolling interests		10	9
Other Cost and Expense, Operating		(19)	(1)
L&S
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)		(129)	(130)
L&S | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[2]	1,026	904
Income from equity method investments		71	52
G&P
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)		(167)	(183)
G&P | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[2]	493	489
Income from equity method investments		$ 63	$ 47

[1] Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

[2] 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
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Capitalized interest	$ 3	$ 2
Gross PP&E	26,083		$ 25,911
Accumulated Depreciation	7,325		7,063
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	18,758		18,848
L&S
Property, Plant and Equipment [Line Items]
Gross PP&E	12,476		12,416
Accumulated Depreciation	3,673		3,554
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	8,803		8,862
G&P
Property, Plant and Equipment [Line Items]
Gross PP&E	13,607		13,495
Accumulated Depreciation	3,652		3,509
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	$ 9,955		$ 9,986

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Fair Values - Recurring - Balance Sheet Location Table (Details) - USD ($) $ in Millions	Mar. 31, 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	58	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	11	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	$ 47	$ 51

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Fair Values - Recurring - Significant Unobservable Inputs in Level 3 Valuation (Details)	3 Months Ended
	Mar. 31, 2023 USD ($) $ / gal
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Average Forward Price | $ / gal	0.77
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	0.58
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	1.55

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Changes in Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (61)	$ (108)
Unrealized and realized gain included in Net Income(1)	[1]	0	4
Settlements		3	5
Ending balance		$ (58)	$ (99)

[1] Gain/(loss) 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
	Mar. 31, 2023	Mar. 31, 2022
Fair Value Disclosures [Abstract]
The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$ 0	$ 5

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Fair Values - Reported (Details) - USD ($) $ in Millions		Mar. 31, 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]	$ 19,167	$ 18,095
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 20,517	$ 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)	Mar. 31, 2023 gal
Propane | Short | Over-the-Counter
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	33,970,000

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Derivative Financial Instruments - Embedded Derivatives in Commodity Contracts (Details) - Embedded Derivative Financial Instruments [Member] $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Liability	$ (58)	$ (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	Mar. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 58	$ 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	11	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	$ 47	$ 51

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Derivatives Financial Instruments - Derivative Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 2	$ 4
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Purchased product costs
Derivative [Line Items]
Realized gain (loss)	$ (3)	$ (5)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	3	9
Derivative, Gain (Loss) on Derivative, Net	0	4
Product Sales
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	2	0
Derivative, Gain (Loss) on Derivative, Net	$ 2	$ 0

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Debt - Summary of Outstanding Borrowings (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
MPLX Credit Agreement	$ 0	$ 0
Financing lease obligations	7	8
Debt and Lease Obligation	20,707	20,108
Unamortized debt issuance costs	(130)	(117)
Unamortized discount	(183)	(195)
Amounts due within one year	1	988
Total long-term debt due after one year	20,393	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	Mar. 31, 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	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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
		Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer, Other	[1]	$ 586	$ 476
Revenues		2,713	2,610
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2,127	2,134
L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,038	987
L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,460	1,337
G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,089	1,147
G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,253	1,273
Service [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		953	915
Service [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		83	72
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		950	911
Service [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,033	983
Service [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		522	482
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		3	4
Service [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		525	486
Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Service, Other [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0
Service, Other [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Product [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		70	45
Product [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2	1
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		3	3
Product [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5	4
Product [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		418	496
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		67	42
Product [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 564	$ 661

[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 $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

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Revenue Contract Balances (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Contract with Customer, Asset, before Allowance for Credit Loss		$ 16	$ 7	$ 21	$ 25
Contract assets, additions/(deletions)		(5)	(18)
Contract with Customer, Asset, Reclassified to Receivable	[1]	0	0
Contract with Customer, Asset, before Allowance for Credit Loss, Noncurrent		0	2	1	2
Contract with Customer, Asset Increase (Decrease), Noncurrent		(1)	0
Contract With Customer Non Current Asset Reclassified To Receivable [Line Items]	[1]	0	0
Contract Liability, Current, Revenue Recognized		0
Contract Liability, Current, Period Increase (Decrease)		1
Contract with Customer, Liability, Current		1		0
Long-term deferred revenue		233		219
Contract with Customer, Liability, Noncurrent		0	5	2	5
Contract Liability, Noncurrent, Period Increase (Decrease)		(2)	0
Contract Liability, Noncurrent, Revenue Recognized	[1]	0	0
Liability, change in timeframe, performance obligation satisfied, revenue recognized		0	0
Nonrelated Party [Member]
Deferred revenue		45	58	57	56
Deferred revenue, revenue recognized	[1]	(14)	(9)
Deferred Revenue, Additions		2	11
Long-term deferred revenue		231	137	216	135
Long-term deferred revenue, additions/(deletions)		15	2
Long-term deferred revenue, revenue recognized	[1]	0	0
Related Party [Member]
Deferred revenue		87		80
Deferred revenue, revenue recognized	[1]	(26)	(26)
Deferred Revenue, Additions		32	34
Deferred Revenue from Contracts with Customers, Current		69	68	63	60
Long-term deferred revenue		111		110
Long-term deferred revenue, additions/(deletions)		1	0
Long-term deferred revenue, revenue recognized	[1]	0	0
Deferred Revenue from Contracts with Customers, Noncurrent		$ 26	$ 31	$ 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	Mar. 31, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Contract with customer, liability	$ 370
Revenue, Remaining Performance Obligation, Amount	8,068	[1],[2],[3]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,346
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,680
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,589
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,433
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	3 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,312
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	4 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 708
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	5 years
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	21 years

[1] All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded.

[2] Only minimum volume commitments that are deemed fixed are included in the table above. MPLX has various minimum volume commitments in processing arrangements that vary based on the actual Btu content of the gas received. These amounts are deemed variable consideration and are excluded from the table above.

[3] Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

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Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Other Significant Noncash Transactions [Line Items]
Interest paid (net of amounts capitalized)	$ 270	$ 213
Income taxes paid	1	0
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	9	0
Reclassification, Other
Other Significant Noncash Transactions [Line Items]
Property, Plant and Equipment, Transfers and Changes	$ 28	$ 10

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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	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment	$ 169	$ 169
Increase in capital accruals	22	3
Capital Expenditure	$ 191	$ 172

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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
	Dec. 15, 2020	Jul. 31, 2020	Mar. 31, 2023	Dec. 31, 2022
Commitments And Contingencies [Line Items]
Accrued liabilities for environmental remediation			$ 17	$ 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 a joint venture 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. 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 EIS has been delayed and the Army Corps currently expects to release a draft EIS in 2023.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 pipeline were temporarily shut down, 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 permit and/or return the pipeline into operation. If the vacatur of the easement permit 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 March 31, 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