Exhibit 23.1 INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in this Registration Statement of Premcor Inc. on Form S-8 of our report dated February 11, 2002 (March 29, 2002 as to Note 15 and April 15, 2002 as to Notes 10 and 19), appearing in Registration Statement No. 333-70314 on Form S-1 of Premcor Inc., and of our report dated February 11, 2002 relating to the financial statement schedules also appearing in Registration Statement No. 333-70314. /s/ Deloitte & Touche - --------------------- St. Louis, Missouri April 29, 2002