Valero is one of the US' largest retail operators with approximately 6,800 retail and branded wholesale outlets in the US, Canada, UK, and the Caribbean under the Valero, Diamond Shamrock, Shamrock, Ultramar, Beacon, and Texaco brands.
CITGO, based in Houston, is a refiner, transporter and marketer of transportation fuels, lubricants, petrochemicals and other industrial products.
ConocoPhillips is the world's largest independent exploration and production company, based on proved reserves and production of liquids and natural gas. The company explores, develops, and produces crude oil and natural gas globally.
Phillips 66 is a Houston-based American multinationalenergy company with 15 refineries with a net crude oil capacity of 2.2 million barrels per day, 10,000 branded marketing outlets, and 15,000 miles of pipelines.
Shell is a vertically integrated O&G company with products including refining, distribution and petrochemicals. It produces around 3.1 million barrels of oil equivalent per day and has 44,000 service stations worldwide.