UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

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¨ Preliminary Proxy Statement

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¨ Definitive Proxy Statement

þ Definitive Additional Materials

¨ Soliciting Material Pursuant to §240.14a-12

TESORO CORPORATION

(Name of Registrant as Specified in Its Charter)

Name of Person(s) Filing Proxy Statement if other than the Registrant)

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Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting

to be held on May 3, 2016, for Tesoro Corporation

This communication is not a form of voting and presents only an overview of the more complete proxy materials, which contain important information and are available to you on the Internet or by mail. We encourage you to access and review all of the information contained in the proxy materials before voting. To view the proxy statement and annual report, go to www.proxydocs.com/tso. To submit your proxy while visiting this site, you will need the 12 digit control number in the box below.

Under United States Securities and Exchange Commission rules, proxy materials do not have to be delivered in paper. Proxy materials can be distributed by making them available on the Internet. We have chosen to use these procedures for our 2016 Annual Meeting and need YOUR participation.

If you want to receive a paper or e-mail copy of the proxy materials, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed below on or before April 20, 2016 to facilitate timely delivery.

For a Convenient Way to VIEW Proxy Materials – and – VOTE Online go to: www.proxydocs.com/tso

Proxy materials may be requested by one of the following methods:

INTERNET     www.investorelections.com/tso	TELEPHONE (866) 648-8133		*E-MAIL paper@investorelections.com
You must use the 12 digit control number located in the shaded gray box below.		*  If requesting material by e-mail, please send a blank e-mail with the 12 digit control number (located below) in the subject line. No other requests, instructions or other inquiries should be included with your e-mail requesting material.

ACCOUNT NO.   SHARES  

Tesoro Corporation Notice of Annual Meeting

Date:	Tuesday, May 3, 2016
Time:	8:00 A.M. (Central Time)
Location:	Tesoro Corporation, 19100 Ridgewood Parkway, San Antonio, Texas 78259

The purpose of the Annual Meeting is to take action on the following proposals:

The Board of Directors recommends that you vote “FOR” the election of each of the nominees for director.

1.      Election of 10 Directors (all nominated as directors to serve for the term indicated in the proxy statement):
Nominees	01  Rodney F. Chase	03  Gregory J. Goff	05  David Lilley	07  J.W. Nokes	09  Michael E. Wiley
	02  Edward G. Galante	04  Robert W. Goldman	06  Mary Pat McCarthy	08  Susan Tomasky	10  Patrick Y. Yang

The Board of Directors recommends that you vote “FOR” proposals 2 and 3, and against proposal 4.

2. To approve our named executive officers’ compensation in an advisory vote.

3. To ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm for fiscal year 2016.

4. On the stockholder proposal set forth in the proxy statement, if properly presented at the annual meeting.

PLEASE NOTE: YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares, you must vote on the Internet, by telephone or request a paper copy of the proxy materials to receive a proxy card. Directions to the Tesoro Corporation 2016 Annual Meeting are available at www.tsocorp.com under the heading “Investors”.

Vote in Person Instructions: While we encourage stockholders to vote by the means indicated above, a stockholder is entitled to vote in person at the annual meeting. Additionally, a stockholder who has submitted a proxy before the meeting can revoke that proxy by attending the meeting and voting in person.