Exhibit 3.9

                            CERTIFICATE OF AMENDMENT
                                       OF
                     RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                                CLARK USA, INC.
                 ---------------------------------------------
                   Adopted in accordance with the provisions
                 of Section 242 of the General Corporation Law
                            of the State of Delaware
                 ---------------------------------------------


     The undersigned, being the President and Secretary, respectively, of Clark
USA, Inc., a corporation organized and existing under and by virtue of the
General Corporation Law of the State of Delaware (the "Corporation"), do hereby
certify as follows:

     FIRST:  That the Board of Directors of said Corporation, by the unanimous
written consent of its members, filed with the minutes of the board, duly
adopted resolutions proposing and declaring advisable the following amendment to
the Restated Certificate of Incorporation of said Corporation:

     RESOLVED, that the Restated Certificate of Incorporation of Clark USA, Inc.
be amended by changing the first Article thereof so that, as amended, said
Article shall be and read as follows:

     "ARTICLE 1.  The name of the corporation shall be Premcor USA Inc."

     SECOND:  That in lieu of a meeting and vote of Stockholders, the
Stockholders have given unanimous written consent to said amendment in
accordance with the provisions of Section 228 of the General Corporation Law of
the State of Delaware.


     THIRD:  That the aforesaid amendment was duly adopted in accordance with
the applicable provisions of Sections 242 and 228 of the General Corporation Law
of the State of Delaware.

     FOURTH:  That this Certificate of Amendment of the Restated Certificate of
Incorporation shall be effective on May 10, 2000.

     IN WITNESS WHEREOF, the undersigned have executed this certificate this 9th
day of May, 2000.

                                     CLARK USA, INC.



                                     By:  /s/  William C. Rusnack
                                          -----------------------
                                          William C. Rusnack
                                          President


ATTEST:



By:  /s/  Richard A. Keffer
     ----------------------
     Richard A. Keffer
     Secretary

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