Bloomberg photo by Luke Sharrett

Marathon Petroleum Corp., the largest independent oil refiner in the U.S., is exploring a sale of gas station arm Speedway, according to people familiar with the matter.

The retailer, which Marathon Petroleum has said it would seek to spin off, has drawn interest from potential buyers, said the people, who asked to not be identified because the matter isn’t public. Speedway, with about 4,000 stores in the U.S., could be worth $15 billion to $18 billion, including debt, as a standalone company, Marathon Petroleum has said.

No final decision has been made and Marathon Petroleum, which trades under the MPC ticker symbol, could opt to proceed with a spinoff instead of a sale, the people said.

“A spinoff actually creates more value for MPC shareholders than an outright sale,” Manav Gupta, an analyst at Credit Suisse, said Friday in a note to investors. “However, we understand why some investors would have a strong preference for a sale over spinoff given it’s a lower-risk transaction that unlocks value a lot more quickly than a spinoff.”

A representative for Marathon Petroleum declined to comment. Shares rose 1.7 percent at 9:40 a.m. in New York.

Marathon Petroleum announced plans in October to spin off Speedway in a tax-free distribution to shareholders by the end of 2020. Speedway would pay a dividend to Marathon Petroleum, which would use the proceeds from the transaction to pay down the substantial debt incurred in its $23.3 billion merger in 2018 with Andeavor.

While a spin would create more value, it could also take as long as a year for the full benefit to be realized, Gupta said. If the fuel-distribution sector falls out of favor in that period, Speedway’s value could shrink. A “sale eliminates all these market risks as MPC shareholders will see cash come in the door right away,” according to the note.

A spinoff would be tax-free, while an outright sale could lead to $1.5 billion in cash taxes, Credit Suisse said.

The company is also conducting a strategic review of MPLX LP, its publicly traded oil pipeline affiliate. Marathon will provide an update on the status of MPLX in the first quarter and is targeting a spin off of Speedway in the fourth quarter, according to its earnings report Wednesday.

A Speedway sale could generate much larger cash proceeds than a spinoff, “while potentially changing the landscape for the strategic review of MPLX as well,” Justin Jenkins, an analyst at Raymond James, said Jan. 30 in a note to investors.

The refiner decided to split up last year under pressure from investors including Elliott Management Corp. and D.E. Shaw & Co., which had called for an overhaul of the company. Chief Executive Officer Gary Heminger also announced plans to step down.