Tesoro Corporation (NYSE: TSO aka: "Tesoro Petroleum", or simply as "Tesoro") is a Fortune 100 and a Fortune Global 500 company headquartered in Texas at San Antonio, with 2013 annual revenues of $37 billion, and over 5,700 employees worldwide.Tesoro is an independent refiner and marketer of petroleum products, operating six refineries in the Western United States with a combined rated crude oil capacity of approximately 845,000 barrels (134,300 m3) per day.