TSO

Tesoro Corporation

An American petroleum refiner and marketer that turned crude oil into gasoline, diesel, and jet fuel sold through its own gas stations, including ARCO-branded pumps across the western United States. Founded in 1968 by chemical engineer Dr. Robert Van Osdell West Jr., it took its name from the Spanish word for "treasure" and opened its first refinery near Kenai, Alaska — the first commercial refinery in the state. It later rebranded as Andeavor and was absorbed by Marathon Petroleum in 2018.