Tesoro Corporation, a Fortune 100 company, is an independent refiner and marketer of petroleum products. Tesoro, through its subsidiaries, operates six refineries in the western United States with a combined capacity of over 845,000 barrels per day. Tesoro's retail-marketing system includes over 2,200 retail stations under the Tesoro®, Shell®, ARCO® and USA Gasoline™ brands, of which 595 are company operated.