Valero Energy Corporation is a gas and oil refining and retail company. The corporate office of Valero is based in San Antonio, Texas. The company came onto the market on January 1, 1980, as a part of the Coastal States Gas Corporation. Valero operates 18 refineries in Canada, the United States, as well as the Caribbean. The combined throughput capacity of the plants is approximately 3.3 million barrels per day. That's what makes Valero the largest refiner in North America.