Exhibit 24.1 POWER OF ATTORNEY KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Jeffry N. Quinn his true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for him and his name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to the Registration Statement on the Form S-8 of Premcor Inc., as filed under the Securities Act of 1933, as amended (the "Act"), and all subsequent amendments, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorney-in-fact and agent, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorney-in-fact and agent, or his substitutes, may lawfully do or cause to be done by virtue hereof. This power of attorney may be executed on counterparts. SIGNATURE TITLE DATE /s/ Thomas D. O'Malley -------------------------- Thomas D. O'Malley President, Chief Executive Officer and April 30, 2002 Chairman of the Board (principal executive officer) /s/ David I. Foley -------------------------- David I. Foley Director April 30, 2002 /s/ Robert L. Friedman -------------------------- Robert L. Friedman Director April 30, 2002 /s/ Richard C. Lappin -------------------------- Richard C. Lappin Director April 30, 2002 /s/ Stephen I. Chazen -------------------------- Stephen I. Chazen Director April 30, 2002 /s/ Marshall A. Cohen -------------------------- Marshall A. Cohen Director April 30, 2002 /s/ Jefferson F. Allen -------------------------- Jefferson F. Allen Director April 30, 2002 -------------------------- Wilkes McClave III Director April __, 2002