Located just outside El Dorado, Kansas near the scenic Flint Hills, Frontier’s El Dorado Refinery is the state’s largest refinery. Spread over 1,000 acres, this fully integrated modern facility currently employs approximately 400 Frontier personnel and 100 contractors.

Refining began on the site in 1917 during the boom days associated with the discovery of huge oil reserves in the El Dorado area. The operation then consisted of a primitive skimming plant with a daily capacity of 2000 barrels of crude oil. That first plant belonged to the Midland Refining Company, a forerunner of Skelly Oil Company, which was founded in 1919. Skelly merged with Getty Oil Company on January 31, 1977, and Getty was acquired by Texaco Inc. on January 6, 1984. On January 15, 1998, Shell Oil Company and Texaco Inc. formed Equilon Enterprises LLC, combining elements of Shell and Texaco’s Western and Central U. S. refining and marketing, trading, transportation and lubricants businesses. 

On July 1, 1998, El Dorado Refining Company became an Equilon Enterprises facility. On November 17, 1999, the sale of the refinery and connected truck loading facility to Frontier Oil Corporation was completed. Today, the Refinery can process 110,000 barrels of crude oil and 15,000 barrels of natural gas liquids daily.

The refinery is a collection of complex processes. Distillation, desulfurization, fluid catalytic cracking, alkylation, delayed coking, catalytic reforming, isomerization, and sulfur recovery are the processes contributing to a daily production of 60,000 barrels of gasoline, 40,000 barrels of distillate fuels, 900 tons of petroleum coke and 175 tons of elemental sulfur.