|Frontier Oil Corporation (Frontier) is an independent energy company, engaged in crude oil refining and the wholesale marketing of refined petroleum products. The Company operates refineries in Cheyenne, Wyoming and El Dorado, Kansas with a total annual average crude oil capacity of approximately 187,000 barrels per day (bpd). Frontier's Cheyenne Refinery has crude oil capacity of 52,000 bpd on a 12-month average. The Company markets its refined products in the eastern slope of the Rocky Mountain region, which encompasses eastern Colorado (including the Denver metropolitan area), eastern Wyoming and western Nebraska (the Eastern Slope). The Cheyenne Refinery has a coking unit, which allows the refinery to process amounts of heavy crude oil for use as a feedstock. During the year ended December 31, 2009, heavy crude oil constituted approximately 50% of the Cheyenne Refinery's total crude oil charge.