US refineries are processing crude oil at a seasonal record rate with profit margins above average.

Refineries used 15.8 million bpd of crude and other liquids last week, the highest seasonal level in Energy Information Administration weekly data going back to 1989. The profit from processing crude and selling fuels is over $26/bbl, topping the 10-year seasonal average of about $19.

Refineries are set to further increase their operating levels as plants end seasonal maintenance. Strong refinery demand hasn’t stemmed the growth in US crude supplies as production climbed to a three-decade high. Oil prices have dropped more than half from last year’s peak.

“The margins are pretty high so it really makes sense to get back from maintenance as quickly as you can,” said James Williams, an economist at WTRG Economics, an energy-research firm in London, Arkansas. “Refinery runs will stay quite high for the foreseeable future.”

Refinery crude use increased for a third straight week, up 1% from the seven days ended March 13, according to the EIA, the Energy Department’s statistical arm. Plants operated at 89% of their capacity, up from 88.1% the previous week.

US crude oil inventories gained 8.17 million bbl last week to 466.7 million, the highest level in EIA data going back to 1982.

West Texas Intermediate crude, the US benchmark, gained 84 cents to $48.35/bbl at 11:55 a.m. on the New York Mercantile Exchange. Gasoline futures climbed 2.33 cents to $1.823/gal. Ultra-low-sulfur diesel was up 0.57 cent to $1.7122.

The 3-2-1 crack spread, a rough measure of the profit from processing three barrels of oil into two of gasoline and one of diesel, was $26.762/bbl, up 19% from a year earlier.

Regular gasoline averaged $2.421/gal at the pump Tuesday, the lowest since October 2010, according to AAA, the nation’s biggest motoring group.