Valero Energy is one of the largest independent oil refiners in the world, converting crude oil into gasoline, diesel and other fuels without the upstream exploration and production operations that integrated oil majors also run. As a pure refiner, Valero's profitability depends heavily on the crack spread, the difference between the price of crude oil it buys and the price of refined fuel products it sells, rather than on the price of oil itself. The company also has a growing renewable diesel and ethanol business, converting agricultural feedstocks and used cooking oil into lower-carbon fuel alternatives that qualify for various government incentive programs. Refining margins can swing significantly based on seasonal fuel demand, refinery outages across the industry and shifts in the relative supply of different crude oil grades, making Valero's earnings considerably more volatile quarter to quarter than a regulated utility's would be.