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                                                                     Exhibit 3.8
                           CERTIFICATE OF AMENDMENT
                                      OF
                         CERTIFICATE OF INCORPORATION
                                      OF
                                CLARK USA, INC.


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                   Adopted in accordance with the provisions
                   of Section 242 of the General Corporation
                         Law of the State of Delaware

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     I, Maura J. Clark, Executive Vice President of CLARK USA, INC., a
corporation organized and existing under the laws of the State of Delaware (the
"Corporation"), hereby certify as follows:

     FIRST: That the Restated Certificate of Incorporation of the Corporation
was filed with the Secretary of State of the State of Delaware on December 28,
1994 and that Certificates of Amendment thereto were filed with the Secretary of
State of Delaware on February 23, 1995; November 3, 1995; on three (3) occasions
on October 1, 1997; and on January 15, 1998 (as so amended, the "Certificate of
Incorporation").

     SECOND: That Paragraph (m) entitled "Definitions" of the Certificate of
Designations of the Corporation dated October 1, 1997, which forms a part of the
Certificate of Incorporation of the Corporation, has been amended to read as
follows:

          (1)  by deleting the definition of "Permitted Indebtedness" and
substituting in lieu thereof the following:

          "'Permitted Indebtedness' means Indebtedness incurred by the
     Corporation or its Restricted Subsidiaries (i) to renew, extend, refinance
     or refund Indebtedness that is permitted to be incurred pursuant to clauses
     (ii) through (iv) and clause (xi) below; provided, however, that such
     Indebtedness does not exceed the principal amount of the Indebtedness so
     renewed, extended, refinanced or refunded plus the amount of any premium
     required to be paid in connection with such refinancing pursuant to the
     terms of the Indebtedness
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     refinanced or the amount of any premium reasonably determined by the
     Corporation or such Restricted Subsidiary as necessary to accomplish such
     refinancing by means of a tender offer or privately negotiated repurchase,
     plus the expenses of the Corporation or such Restricted Subsidiary incurred
     in connection with such refinancing; and provided, however, that
     Indebtedness the proceeds of which are used to refinance or refund such
     Indebtedness shall only be permitted if (A) in the case of any refinancing
     or refunding of Indebtedness that is pari passu with the Exchange
     Debentures the Refinancing or refunding Indebtedness is made pari passu
     with the Exchange Debentures or subordinated to the Exchange Debentures,
     (B) in the case of any refinancing or refunding of Indebtedness that is
     subordinated to the Exchange Debentures the refinancing or refunding of
     Indebtedness is made subordinated to the Exchange Debentures at least to
     the same extent as such Indebtedness being refinanced or refunded was
     subordinated to the Exchange Debentures and (C) in the case of the
     refinancing or refunding of Indebtedness that is subordinated to the
     Exchange Debentures, the refinancing or refunding Indebtedness by its
     terms, or by the terms of any agreement or instrument pursuant to which
     such Indebtedness is issued, (x) does not provide for payments of principal
     of such Indebtedness at the stated maturity thereof or by way of a sinking
     fund applicable thereto or by way of any mandatory redemption, defeasance,
     retirement or repurchase thereof by the Corporation or such Restricted
     Subsidiary (including any redemption, retirement or repurchase which is
     contingent upon events or circumstances, but excluding any retirement
     required by virtue of acceleration of such Indebtedness upon an event of
     default thereunder), in each case prior to the final Stated Maturity of the
     Exchange Debentures and (y) does not permit redemption or other retirement
     (including pursuant to an offer to purchase made by the Corporation or such
     Restricted Subsidiary) of such Indebtedness at the option of the holder
     thereof prior to the final stated maturity of the Indebtedness being
     refinanced or refunded, other than a redemption or other retirement at the
     option of the holder of such Indebtedness (including pursuant to an offer
     to purchase made by the Corporation or such Restricted Subsidiary), which
     is conditioned upon the change of control of the Corporation or such
     Restricted Subsidiary); (ii) arising from time to time under the Credit
     Agreement or any refinancings, renewals, extensions, refundings or
     replacements thereof or extensions of credit to finance working capital
     requirements in an aggregate principal amount not to exceed the greater of
     (a) $700 million at any one time outstanding less the aggregate amount of
     all proceeds of all asset dispositions that have been applied since the
     Issue Date to permanently reduce the outstanding amount of such
     Indebtedness and (b) the amount of the Borrowing Base on such date
     (calculated on a pro forma basis after giving effect to such borrowing and
     the application of the proceeds therefrom); (iii) outstanding on the Issue
     Date; (iv) evidenced by trade letters of credit incurred in the ordinary
     course of business not to exceed $20 million in the aggregate at any time;
     (v) between or among the Corporation and/or its Restricted Subsidiaries
     other than Restricted Subsidiaries owned in any part by the Principal
     Shareholders; (vi) which is Junior Subordinated Indebtedness; (vii) arising
     out of Sale and Leaseback Transactions or Capitalized Lease Obligations
     relating to computers and other office equipment and elements, catalysts or
     other chemicals used in connection with the refining of petroleum or
     petroleum by-products; (viii) the proceeds of which are used to make the
     Chevron Payment, the AOC Payment and the Gulf Payments; (ix) arising out of
     Interest Swap Obligations; (x) in connection with capital projects
     qualifying under Section 142(a) (or any successor provision) of the
     Internal Revenue Code of 1986, as amended, in an amount not to exceed $75
     million in the aggregate at any time; (xi) to finance the Lima Acquisition,
     in an amount not to exceed $250 million; and (xii) in addition to
     Indebtedness permitted by clauses (i) through (xi) above, Indebtedness not
     to exceed on a consolidated basis for the Corporation and its Restricted
     Subsidiaries at any time $50 million."; and

          (2)  by adding the following definition in appropriate alphabetical
               order:

          "'Lima Acquisition' means the acquisition by Clark Refining &
     Marketing, Inc. of the Lima Oil Refinery located in Lima, Ohio, and certain
     related inventory, spare parts and other assets, pursuant to the Agreement
     for the Purchase and Sale of Lima Oil Refinery, dated as of July 1, 1998,
     among Clark Refining & Marketing, Inc. and BP Exploration & Oil Inc., The
     Standard Oil Company, BP Oil Pipeline Company and BP Chemicals Inc."
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     THIRD: That such amendment has been duly adopted in accordance with the
provisions of the General Corporation Law of the State of Delaware by the
written consent of the holders of a majority of all outstanding shares of each
class entitled to vote thereon in accordance with the provisions of Section 228
of the General Corporation Law.

     IN WITNESS WHEREOF, the undersigned has signed the Certificate this 31st
day of July, 1998.

                                                     CLARK USA, INC.

By: /s/ Maura J. Clark
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        Maura J. Clark
        Executive Vice President - Corporate
        Development and Chief Financial Officer


Attested By:

/s/ Katherine D. Knocke
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Katherine D. Knocke
Secretary