Updates shares, adds details on the results, outlook and graphic in paragraphs 3, 8-11

May 5 (Reuters) - Marathon Petroleum MPC.N on Tuesday beat Wall Street estimates for first-quarter profit, benefiting from stronger refining margins amid tighter global supply driven by the Middle East war.

Its shares rose 1% in premarket trading, with the stock up 55% so far this year.

The company also approved an additional $5 billion share repurchase program, bringing the total remaining authorization to about $8.6 billion. Marathon returned more than $1 billion to shareholders during the quarter.

U.S. refined products exports hit a record high in March as the Iran war and the near-closure of the Strait of Hormuz tightened global fuel supplies, forcing output cuts abroad and supporting margins for U.S. refiners, which are less reliant on Middle Eastern crude and are well placed to capture demand through exports.

Marathon Petroleum, the top U.S. refiner by volume, said refining and marketing margin was $17.74 per barrel for the first quarter of 2026, versus $13.38 per barrel last year.

It reported crude capacity utilization of 89%, resulting in total throughput of 2.9 million barrels per day (bpd) in the first quarter. This compared with utilization of 89% and throughput of 2.8 million bpd a year earlier.

First-quarter results were partly offset by higher operating costs linked to refinery turnaround activity and derivative losses tied to economic hedging.

For the second quarter, Marathon expects throughput of 2.99 million bpd.

It also expects to spend $1.5 billion in 2026, with most of it going toward projects that improve margins at key refineries.

In the first quarter of 2026, Marathon also brought its Garyville jet flexibility project online, enabling it to upgrade existing output into higher-value jet fuel and capture rising domestic and export demand.

The Findlay, Ohio-based refiner reported adjusted profit of $1.65 per share for the quarter ended March 31, beating analysts' average estimate of 75 cents per share, according to data compiled by LSEG.