Description Frontier Oil's marketing territory covers the old frontier of the Rocky Mountains and the Great Plains. The company refines crude oil and markets petroleum products. Frontier's Cheyenne, Wyoming, refinery can handle 52,000 barrels of heavy crude oil per day, and it processes 135,000 barrels of oil per day at its refinery in El Dorado, Kansas. Both refineries, which produce diesel, gasoline, and other petroleum products, have the advantage of being able to refine heavier, sulfur rich, less expensive forms of crude. They also produce asphalt. In 2011 the company agreed to be acquired by regional rival Holly in an all-stock "merger of equals" that will create an enterprise with a market value of $7 billion.