EXHIBIT 23.1 CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We consent to the incorporation by reference in this Amendment No. 1 to Registration Statement No. 333-120643 of Frontier Oil Corporation on Form S-4 of our report dated February 19, 2004 relating to the financial statement schedules appearing in the Current Report on Form 8-K, filed on November 19, 2004, of Frontier Oil Corporation. /s/ Deloitte & Touche LLP - ------------------------- DELOITTE & TOUCHE LLP Houston, Texas December 3, 2004