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                                                                    EXHIBIT 4.1

                             SUPPLEMENTAL INDENTURE

         THIS SUPPLEMENTAL INDENTURE is dated as of October 20, 2004. between
CITGO PETROLEUM CORPORATION, a Delaware corporation (the "Company") and THE BANK
OF NEW YORK, as Trustee ("Trustee").

         WHEREAS the Company has heretofore executed and delivered to the
Trustee an Indenture dated as of February 27, 2003 (the "Indenture"), providing
for the issuance of the Company's 11 3/8% Senior Notes due 2011 (the
"Securities"); and

         WHEREAS there are now outstanding under the Indenture Securities in the
aggregate principal amount of $550 million; and

         WHEREAS Section 9.02 of the Indenture provides that the Company and the
Trustee may amend the Indenture with the written consent of the Holders of at
least a majority in aggregate principal amount of the Securities then
outstanding; and

         WHEREAS the Company desires to amend certain provisions of the
Indenture, as set forth in Article 1 of this Supplemental Indenture; and

         WHEREAS the Holders of at least a majority in aggregate principal
amount of the Securities outstanding have consented to the amendments set forth
in this Supplemental Indenture; and

         WHEREAS all things necessary to make this Supplemental Indenture a
valid agreement, in accordance with its terms, have been done.

         NOW THEREFORE, this Supplemental Indenture witnesseth that, for and in
consideration of the premises, it is mutually covenanted and agreed, for the
equal and proportionate benefit of all Holders of the Securities, as follows:

                                   ARTICLE I

                             Amendments To Indenture

                  Section 1.01. Amendments to Article Four. Effective upon the
         date (the "Payment Date") that the Company accepts for purchase and
         pays for all Securities validly tendered pursuant to the Offer to
         Purchase and Consent Solicitation Statement dated as of October 8,
         2004, as subsequently amended, modified or supplemented (unless, prior
         to that time, the Company has terminated this Supplemental Indenture as
         provided in Section 2.07 hereof), Sections 4.02, 4.03, 4.04, 4.05,
         4.06, 4.07, 4.08, 4.09, 4.10, 4.11, 4.12 and 4.15 are hereby amended by
         restating Sections 4.02, 4.03, 4.04, 4.05, 4.06, 4.07, 4.08, 4.09,
         4.10, 4.11, 4.12 and 4.15 in their entirety to read as follows:

                  "Section 4.02. Intentionally Omitted.


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                  Section 4.03. Intentionally Omitted.

                  Section 4.04. Intentionally Omitted.

                  Section 4.05. Intentionally Omitted.

                  Section 4.06. Intentionally Omitted.

                  Section 4.07. Intentionally Omitted.

                  Section 4.08. Intentionally Omitted.

                  Section 4.09. Intentionally Omitted.

                  Section 4.10. Intentionally Omitted.

                  Section 4.11. Intentionally Omitted.

                  Section 4.12. Intentionally Omitted.

                  Section 4.15. Intentionally Omitted."

                  Section 1.02. Amendments to Article Five. Effective upon the
         Payment Date (unless, prior to that time, the Company has terminated
         this Supplemental Indenture as provided in Section 2.07 hereof),
         Sections 5.01 and 5.02 are hereby amended by restating Sections 5.01
         and 5.02 in their entirety to read as follows:

                  "Section 5.01. When Company may Merge or Transfer Assets. The
         Company shall not consolidate with or merge with or into, or convey,
         transfer or lease, in one transaction or a series of transactions,
         directly or indirectly, all or substantially all its assets to, any
         Person, unless:

                           (1)      the resulting, surviving or transferee
                  Person (the "Successor Company") shall be a Person organized
                  and existing under the laws of the United States of America,
                  any State thereof or the District of Columbia and the
                  Successor Company (if not the Company) shall expressly assume,
                  by an indenture supplemental hereto, executed and delivered to
                  the Trustee, in form satisfactory to the Trustee, all the
                  obligations of the Company under the Securities and this
                  Indenture and

                           (2)      immediately after giving effect to such
                  transaction (and treating any Indebtedness which becomes an
                  obligation of the Successor Company or any Subsidiary as a
                  result of such transaction as having been Incurred by such
                  Successor Company or such Subsidiary at the time of such
                  transaction), no Default shall have occurred and be
                  continuing.

                           (3)      Intentionally Omitted.

                           (4)      Intentionally Omitted.


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                  For purposes of this covenant, the sale, lease, conveyance,
         assignment, transfer or other disposition of all or substantially all
         of the properties and assets of one or more Subsidiaries of the
         Company, which properties and assets, if held by the Company instead of
         such Subsidiaries, would constitute all or substantially all of the
         properties and assets of the Company on a consolidated basis, shall be
         deemed to be the transfer of all or substantially all of the properties
         and assets of the Company.

                  The Successor Company shall be the successor to the Company
         and shall succeed to, and be substituted for, and may exercise every
         right and power of, the Company under this Indenture, and the
         predecessor Company, except in the case of a lease, shall be released
         from the obligation to pay the principal of and interest on the
         Securities.

                  Section 5.02. When Subsidiary Guarantor May Merge or Transfer
         Assets. The Company shall not permit any Subsidiary Guarantor to
         consolidate with or merge with or into, or convey, transfer or lease,
         in one transaction or series of transactions, all or substantially all
         of its assets to any Person unless:

                           (1)      the resulting, surviving or transferee
                  Person (if not such Subsidiary) shall be a Person organized
                  and existing under the laws of the jurisdiction under which
                  such Subsidiary was organized or under the laws of the United
                  States of America, or any State hereof or the District of
                  Columbia, and such Person shall expressly assume, by an
                  amendment or supplemental indenture to this Indenture, in a
                  form acceptable to the Trustee, all the obligations of such
                  Subsidiary, if any, under its Subsidiary Guaranty; provided,
                  however, that the provisions of this Section 5.02(1) shall not
                  apply in the case of a Subsidiary Guarantor that has been
                  disposed of in its entirety to another Person (other than to
                  the Company or an Affiliate of the Company), whether through a
                  merger, consolidation or sale of Capital Stock or assets, if
                  in connection therewith the Company provides an Officers'
                  Certificate to the Trustee to the effect that the Company will
                  comply with its obligations under Section 4.06, if then
                  applicable, in respect of such disposition and

                           (2)      immediately after giving effect to such
                  transaction or transactions on a pro forma basis (and treating
                  any Indebtedness which becomes an obligation of the resulting,
                  surviving or transferee Person as a result of such transaction
                  as having been issued by such Person at the time of such
                  transaction), no Default shall have occurred and be
                  continuing.

                           (3)      Intentionally Omitted."

                  Section 1.03. Amendments to Article Six. Effective upon the
         Payment Date (unless, prior to that time, the Company has terminated
         this Supplemental Indenture as provided in Section 2.07 hereof),
         Section 6.01 is hereby amended by restating Sections 6.01 in its
         entirety to read as follows:

                  "Section 6.01. Events of Default. An "Event of Default" occurs
         if:


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                           (1)      the Company defaults in any payment of
                  interest on any Security when the same becomes due and
                  payable, and such default continues for a period of 30 days;

                           (2)      the Company defaults in the payment of the
                  principal of any Security when the same becomes due and
                  payable at its Stated Maturity, upon optional redemption, upon
                  required purchase, upon declaration of acceleration or
                  otherwise;

                           (3)      the Company fails to comply with Section
                  5.01;

                           (4)      the Company fails to comply with its
                  obligations, if then applicable, in Section 4.15 and such
                  failure continues for 30 days after the notice specified
                  below;

                           (5)      Intentionally Omitted;

                           (6)      Intentionally Omitted;

                           (7)      Intentionally Omitted;

                           (8)      Intentionally Omitted;

                           (9)      Intentionally Omitted; and

                           (10)     any Subsidiary Guaranty ceases to be in full
                  force and effect (other than in accordance with the terms of
                  this Indenture and such Subsidiary Guaranty) or any Subsidiary
                  Guarantor denies or disaffirms its obligations under its
                  Subsidiary Guaranty.

                  The foregoing will constitute Events of Default whatever the
         reason for any such Event of Default and whether it is voluntary or
         involuntary or is effected by operation of law or pursuant to any
         judgment, decree or order of any court or any order, rule or regulation
         of any administrative or governmental body.

                  The term "Bankruptcy Law" means Title 11, United States Code,
         or any similar Federal or state law for the relief of debtors. The term
         "Custodian" means any receiver, trustee, assignee, liquidator,
         custodian or similar official under any Bankruptcy Law.

                  A Default under clause (4) shall not constitute an Event of
         Default until the Trustee or the Holders of at least 25% in principal
         amount of the outstanding Securities notify the Company in writing of
         the Default and the Company does not cure such Default within the time
         specified after receipt of such notice. Such notice must specify the
         Default, demand that it be remedied and state that such notice is a
         "Notice of Default."

                  The Company shall deliver to the Trustee, within 30 days after
         the occurrence thereof, written notice in the form of an Officers'
         Certificate of any event which with the giving of notice or the lapse
         of time would become an Event of Default under clause (4), its status
         and what action the Company is taking or proposes to take with respect
         thereto."



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                                   ARTICLE II

                                  Miscellaneous

         Section 2.01. Instruments To Be Read Together. This Supplemental
Indenture is an indenture supplemental to and in implementation of the
Indenture, and said Indenture and this Supplemental Indenture shall henceforth
be read together.

         Section 2.02. Confirmation. The Indenture, as amended and supplemented
by this Supplemental Indenture, is in all respects confirmed and preserved.

         Section 2.03. Terms Defined. Capitalized terms used in this
Supplemental Indenture have been inserted for convenience of reference only, and
are not to be considered a part hereof and shall in no way modify or restrict
any of the terms and provisions hereof.

         Section 2.04. Headings. The headings of the Articles and Sections of
this Supplemental Indenture have been inserted for convenience of reference
only, and are not to be considered a part hereof and shall in no way modify or
restrict any of the terms and provisions hereof.

         Section 2.05. Governing Law. The laws of the State of New York shall
govern this Supplemental Indenture.

         Section 2.06. Counterparts. This Supplemental Indenture may be executed
in any number of counterparts, each of which so executed shall be deemed to be
an original, but all such counterparts shall together constitute but one and the
same instrument.

         Section 2.07. Effectiveness; Termination. The provisions of this
Supplemental Indenture will take effect immediately upon its execution and
delivery by the Trustee in accordance with the provisions of Sections 9.02 and
9.06 of the Indenture; provided, that the amendments to the Indenture set forth
in Article I of this Supplemental Indenture shall become operative as specified
in Article I hereof. Prior to the Payment Date, the Company may terminate this
Supplemental Indenture upon written notice to the Trustee. Upon receipt by the
Trustee of any such notice of termination, this Supplement Indenture shall be
deemed terminated and of no further force or effect.

         Section 2.08. Acceptance by Trustee. The Trustee accepts the amendments
to the Indenture effected by this Supplemental Indenture and agrees to execute
the trusts created by the Indenture as hereby amended, but only upon the terms
and conditions set forth in the Indenture.

         Section 2.09. Responsibility of Trustee. The recitals contained herein
shall be taken as the statements of the Company, and the Trustee assumes no
responsibility for their correctness. The Trustee makes no representations as to
the validity or sufficiency of this Supplemental Indenture.


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         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed, all as of the date first written above.

                                         CITGO PETROLEUM CORPORATION



                                         By: /s/ Philip J. Reedy
                                            -----------------------------------
                                            Name:  Philip J. Reedy
                                            Title: Treasurer

                                           THE BANK OF NEW YORK



                                         By: /s/ Steven D. Torgeson
                                            -----------------------------------
                                            Name:  Steven D. Torgeson
                                            Title: Vice President