Marathon's stock at last check was off 2% to $66.19.
The moves come as activist investors Elliott Management and DE Shaw have ramped up pressure on Marathon Petroleum to make major changes and boost its financial performance.
The Speedway chain of gas stations is expected to post earnings before interest, taxes, depreciation and amortization of $1.9 billion for 2019, Marathon said in a statement. Same-store sales have grown and fuel profit margins have widened, Marathon said.
The company has also begun an internal and external search for a new CEO for Speedway.
In addition, Marathon plans to assess how to best build value for its midstream assets.
Marathon CEO Gary Heminger will retire next year, the company's said. He started with the company in the mid-1970s and has been at the top since 2011.
Heminger oversaw the $23 billion acquisition of rival Andeavor more than a year ago, making Marathon Petroleum the second-largest independent refiner.
Elliott, the hedge fund owned by Paul Singer, has pushed Marathon Petroleum to split into three, including logistics and retail, arguing that the move would unlock as much as $40 billion in shareholder value.
Withal, the Findlay, Ohio, company's third-quarter earnings beat quarterly estimates.
In the third-quarter MPC earned $1.66 a share compared with $1.62 in the year-earlier quarter. Revenue rose 35% to $31.2 billion.
A survey of analysts by FactSet was looking for profit of $1.53 a share on revenue of $32.74 billion.
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