Exhibit 99.1

Marathon Petroleum Corporation Reports Second-Quarter 2014 Results

FINDLAY, Ohio, July 31, 2014 – Marathon Petroleum Corporation (NYSE: MPC) today reported 2014 second-quarter earnings of $855 million, or $2.95 per diluted share, compared with $593 million, or $1.83 per diluted share, for the second quarter of 2013. Second-quarter 2014 earnings included pretax pension settlement expenses of $5 million, compared with $60 million for the second quarter of 2013.

“We had an outstanding quarter, with our focus on top-tier operational performance across the MPC refining, marketing and transportation system continuing to yield excellent results,” said President and CEO Gary R. Heminger. “Our integrated system operated very well, enabling us to efficiently meet consumers’ needs and capture higher product price realizations in the markets where we do business.

“I’m especially pleased with our smooth ramp-up following the largest combined turnaround activity in our history, which we executed in the first quarter,” added Heminger, “and the tremendous response by our team in Garyville, La., to bring the facility back on line quickly after it was hit by a tornado in late May.”

Heminger noted that balancing return of capital to shareholders with investments in the business remains a priority. MPC purchased $459 million of its shares in the second quarter. On July 30, the MPC board of directors authorized up to an additional $2 billion of share repurchases through July 2016 and increased the quarterly dividend to $0.50 per share. During the 12 months ended June 30, MPC returned $3.1 billion of capital to shareholders, representing a yield against average share price of 13.5 percent.

“We also have made excellent progress on our strategic priority of growing our higher-valued, stable cash-flow businesses as we continue returning capital to shareholders,” said Heminger. In the midstream, he noted that MPC recently exercised its option to acquire a 35 percent ownership interest in Enbridge Inc.’s Southern Access Extension pipeline project. This investment positions MPC as an equity owner in a system that will increase MPC’s access to crude oil from an important region for North American production. The Southern Access Extension pipeline is expected to be in service mid-2015. MPC expects to invest approximately $295 million in the pipeline project.

On the retail side, Heminger said MPC has received notice that the Federal Trade Commission has concluded its review of the acquisition of Hess Retail Holdings LLC by MPC subsidiary Speedway LLC, which continues to prepare for a closing later this year. The company anticipates the acquisition will be a source of long-term value to MPC, resulting in Speedway growing to more than 2,700 stores in 23 states, and also adding transport operations and shipper history on various pipelines.

Segment Results

Total income from operations was $1.37 billion in the second quarter of 2014, compared with $960 million in the second quarter of 2013.

Refining & Marketing

Refining & Marketing segment income from operations was $1.26 billion in the second quarter of 2014, compared with $903 million in the second quarter of 2013. The increase was primarily due to more favorable net product price realizations and a higher U.S. Gulf Coast crack spread, partially offset by a narrower West Texas Intermediate/Light Louisiana Sweet (WTI/LLS) crude oil differential and a lower Chicago crack spread. The company believes the second-quarter 2013 product price realizations compared to spot market values were negatively impacted by volatility in the Chicago market and effects of the Renewable Fuel Standard. The Gulf Coast LLS 6-3-2-1 crack spread in the second quarter of 2014 increased by $2.55 per barrel compared to the second quarter of 2013. The WTI/LLS crude oil differential narrowed by $8.09 per barrel and the Chicago 6-3-2-1 crack spread decreased by $2.72 per barrel when compared to the second quarter of 2013.

Speedway

Speedway segment income from operations was $94 million in the second quarter of 2014, compared with $123 million in the second quarter of 2013. Speedway’s merchandise sales, as well as the margin percentage realized on those sales, were higher in the second quarter of 2014 compared to the second quarter of 2013. Speedway experienced a lower gasoline and distillate gross margin and higher operating expenses associated with an increase in the number of Speedway stores compared to 2013. The gasoline and distillate gross margin per gallon decreased 4.56 cents, from 17.38 cents in the second quarter of 2013 to 12.82 cents in the second quarter of 2014.

Pipeline Transportation

Pipeline Transportation segment income from operations, including 100 percent of MPLX LP’s operations, was $81 million in the second quarter of 2014, compared with $58 million for the second quarter of 2013. The increase was primarily due to higher pipeline transportation revenue and equity affiliate income associated with MPC’s investment in LOOP LLC.

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Items Not Allocated to Segments

Corporate and other unallocated expenses of $61 million in the second quarter of 2014 were consistent with the second quarter of 2013. During the second quarter of 2014, MPC recorded pretax pension settlement expenses of $5 million resulting from the level of employee lump-sum retirement distributions occurring in 2014, compared with $60 million of pretax pension settlement expenses in the second quarter of 2013.

Strong Financial Position and Liquidity

On June 30, the company had $2.1 billion in cash and cash equivalents, an unused $2.5 billion revolving credit agreement and a $1.3 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 June 30, the company’s strong financial position was reflected by its debt-to-total capital ratio of 25 percent.

Conference Call

At 10 a.m. EDT today, MPC will hold a webcast and conference call to discuss the reported results 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 “2014 Second-Quarter Financial Results” link. Replays of the conference call will be available on the company’s website through Wednesday, Aug. 13. 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 5,300 independently owned retail outlets across 19 states. In addition, Speedway LLC, an MPC subsidiary, owns and operates the nation’s fourth-largest convenience store chain, with approximately 1,490 convenience stores in nine 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:

Beth Hunter (419) 421-2559

Geri Ewing (419) 421-2071

Media Contacts:

Angelia Graves (419) 421-2703

Jamal Kheiry (419) 421-3312

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References to Earnings

References to earnings mean net income attributable to 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: our ability to successfully complete the acquisition of Hess Retail Holdings LLC and to integrate the acquired retail operations and achieve the strategic and other expected objectives relating to the proposed acquisition, including any expected synergies; changes to the expected construction costs of the Southern Access Extension pipeline; 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 authorizations, including the timing and amounts of any common stock repurchases; state and federal environmental, economic, health and safety, energy and other policies and regulations, including the cost of compliance with the Renewable Fuel Standard; 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 Dec. 31, 2013, 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.

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Consolidated Statements of Income (Unaudited)

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Supplemental Statistics (Unaudited)

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Supplemental Statistics (Unaudited) (continued)

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Supplemental Statistics (Unaudited) (continued)

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

Select Financial Data (Unaudited)

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