Exhibit 99.1

Marathon Petroleum Corporation Reports First-Quarter 2013 Results

FINDLAY, Ohio, April 30, 2013 – Marathon Petroleum Corporation (NYSE: MPC) today reported first-quarter earnings of $725 million, or $2.17 per diluted share, compared with $596 million, or $1.70 per diluted share, in the first quarter of 2012.

“Our performance this quarter reflects in large part the strategic expansion and optimization of our refining system along with favorable market conditions,” said MPC President and Chief Executive Officer Gary R. Heminger. The first quarter of 2013 marks the first full quarter since completion of MPC’s Detroit Heavy Oil Upgrade Project (DHOUP). In addition, MPC finalized the acquisition of the Galveston Bay refinery and related assets on Feb. 1.

Heminger highlighted the performance of the Detroit refinery, saying, “Since bringing the new units online and quickly reaching the design capacity, the DHOUP expansion has provided our system with greater flexibility to refine larger volumes of price-advantaged crudes, including Canadian heavy.”

“Our Galveston Bay refinery is well positioned on the Texas Gulf Coast to process growing supplies of North American crude oil,” Heminger added. “With its array of complex processing units, we continue to be enthusiastic about our prospects to enhance margins and further leverage dynamic market trends through this strategic acquisition.”

Heminger also noted that Speedway had a strong quarter, primarily due to higher fuel margins and additional revenue from stores acquired last year.

MPC continues to balance investments in the business with returning capital to shareholders. During the first quarter, the company returned $547 million to shareholders through share repurchases and the payment of $116 million of dividends. At the end of the first quarter, a total of $2.2 billion remained under an existing share repurchase authorization.

As MPLX LP (MPLX) announced today, it will acquire an additional 5 percent interest in MPLX Pipe Line Holdings LP from a subsidiary of MPC for $100 million on May 1. This will bring MPLX’s interest to 56 percent from the 51 percent interest it held since its initial public offering (IPO) in October 2012. Heminger noted this is the first drop-down following the IPO and said this transaction, and the increase in MPLX’s quarterly distribution announced earlier today, demonstrate MPC’s commitment to support the growth of MPLX.

Segment Results

Total income from operations was $1.16 billion in the first quarter of 2013, compared with $956 million in the first quarter of 2012.

Refining & Marketing

Refining & Marketing segment income from operations was $1.11 billion in the first quarter of 2013, compared with $943 million in the first quarter of 2012. The increase was primarily due to higher refined product production and sales volumes, attributable in large part to the acquisition of the Galveston Bay refinery on Feb. 1, 2013. Refining & Marketing’s refined product sales volumes were 1.88 million barrels per day (bpd) in the first quarter of 2013, compared with 1.53 million bpd in the first quarter of 2012. The favorable production and sales volumes impact was partially offset by a slight decrease in the Refining & Marketing gross margin, which was $7.92 per barrel in the first quarter of 2013, compared with $8.36 per barrel in the first quarter of 2012. MPC’s benchmark Light Louisiana Sweet (LLS) crack spread was higher in the first quarter of 2013 compared to the first quarter of 2012. However, MPC experienced higher operating and turnaround costs in the first quarter of 2013 compared to the first quarter of 2012. In addition, MPC’s average crude oil acquisition discount narrowed compared to LLS in the first quarter of 2013.

Speedway

Speedway segment income from operations was $67 million in the first quarter of 2013, compared with $50 million in the first quarter of 2012. The $17 million increase was primarily the result of a higher gasoline and distillates gross margin and a higher merchandise gross margin, partially offset by higher expenses associated with the increase in the number of stores operated. Speedway gasoline and distillates gross margin per gallon averaged 13.01 cents in the first quarter of 2013, compared with 10.96 cents in the first quarter of 2012.

Pipeline Transportation

Pipeline Transportation segment income from operations, including 100 percent of MPLX’s operations, was $51 million in the first quarter of 2013, compared with $42 million in the first quarter of 2012. The increase in segment income was primarily due to an increase in transportation revenue and pipeline affiliate income, partially offset by an increase in mechanical integrity and depreciation expenses.

Corporate Items

Corporate and other unallocated expenses of $67 million in the first quarter of 2013 were $12 million lower than in the first quarter of 2012. The decrease was primarily due to a decrease in pension expenses resulting from a pension plan amendment adopted in the second quarter of 2012.

Strong Financial Position and Liquidity

On March 31, 2013, the company had $4.7 billion in cash and cash equivalents, an unused $2.5 billion revolving credit agreement and a $1 billion unused trade receivables securitization facility. The company’s credit facilities and cash position should provide it with sufficient flexibility to meet its day-to-day operational needs and continue its balanced approach to investing in the business and returning capital to shareholders. As of March 31, 2013, the company’s strong financial position was further reflected by its debt-to-total-capital ratio of 22 percent.

Conference Call

At 10 a.m. EDT today, MPC will hold a webcast and conference call to discuss the earnings release and provide an update on company operations. Interested parties may listen to the conference call on MPC’s website at http://www.marathonpetroleum.com by clicking on the “2013 First-Quarter Financial Results” link. Replays of the conference call will be available on the company’s website through Wednesday, May 15. Financial information, including the earnings release and other investor-related material, will also be available online prior to the webcast and conference call at http://ir.marathonpetroleum.com in the Quarterly Investor Packet and Earnings Capsule.

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About Marathon Petroleum Corporation

MPC is the nation’s fourth-largest refiner, with a crude oil refining capacity of approximately 1.7 million barrels per calendar day in its seven-refinery system. Marathon brand gasoline is sold through approximately 5,000 independently owned retail outlets across 17 states. In addition, Speedway LLC, an MPC subsidiary, owns and operates the nation’s fourth-largest convenience store chain, with approximately 1,460 convenience stores in seven states. MPC also owns, leases or has ownership interests in approximately 8,300 miles of pipeline. Through subsidiaries, MPC owns the general partner of MPLX LP, a midstream master limited partnership. MPC’s fully integrated system provides operational flexibility to move crude oil, feedstocks and petroleum-related products efficiently through the company’s distribution network in the Midwest, Southeast and Gulf Coast regions. For additional information about the company, please visit our website at http://www.marathonpetroleum.com.

Investor Relations Contacts:

Pamela Beall (419) 429-5640

Beth Hunter (419) 421-2559

Media Contacts:

Angelia Graves (419) 421-2703

Jamal Kheiry (419) 421-3312

References to Earnings

References to earnings mean net income attributable to Marathon Petroleum Corporation (MPC) from the statements of income. Unless otherwise indicated, references to earnings and earnings per share are MPC’s share after excluding amounts attributable to noncontrolling interests.

Forward-looking Statements

This press release contains forward-looking statements within the meaning of federal securities laws. These forward-looking statements relate to, among other things, MPC’s expectations, estimates and projections concerning MPC business and operations. You can identify forward-looking statements by words such as “anticipate,” “believe,” “estimate,” “expect,” “forecast,” “project,” “could,” “may,” “should,” “would,” “will” or other similar expressions that convey the uncertainty of future events or outcomes. Such forward-looking statements are not guarantees of future performance and are subject to risks, uncertainties and other factors, some of which are beyond MPC’s control and are difficult to predict. Factors that could cause actual results to differ materially from those in the forward-looking statements include: volatility in and/or degradation of market and industry conditions; the availability and pricing of crude oil and other feedstocks; slower growth in domestic and Canadian crude supply; completion of pipeline capacity to areas outside the U.S. Midwest; consumer demand for refined products; transportation logistics; the reliability of processing units and other equipment; our ability to

successfully implement growth opportunities; impacts from our repurchases of shares of MPC common stock under our share repurchase authorization, including the timing and amounts of any common stock repurchases; our ability to successfully complete or realize the strategic benefits of the sale of an additional 5 percent interest in MPLX Pipe Line Holdings LP to MPLX LP; state and federal environmental, economic, health and safety, energy and other policies and regulations; other risk factors inherent to our industry; and the factors set forth under the heading “Risk Factors” in MPC’s Annual Report on Form 10-K for the year ended December 31, 2012 filed with the Securities and Exchange Commission (SEC). In addition, the forward-looking statements included herein could be affected by general domestic and international economic and political conditions. Unpredictable or unknown factors not discussed here or in MPC’s Form 10-K could also have material adverse effects on forward-looking statements. Copies of MPC’s Form 10-K are available on the SEC website, MPC’s website at http://ir.marathonpetroleum.com or by contacting MPC’s Investor Relations Office.

Consolidated Statements of Income (Unaudited)

Supplemental Statistics (Unaudited)

Supplemental Statistics (Unaudited) (continued)

Segment Earnings Before Interest, Taxes, Depreciation & Amortization (Segment EBITDA) (Unaudited)

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