<PAGE>

                                                                    EXHIBIT 10.6

================================================================================

                        THIRD AMENDMENT TO LOAN AGREEMENT
                              AND OMNIBUS AMENDMENT

                          Dated as of December 20, 2002

                                  in respect of

                              GIANT YORKTOWN, INC.

================================================================================

<PAGE>

                                 THIRD AMENDMENT
                                TO LOAN AGREEMENT
                              AND OMNIBUS AMENDMENT

         This THIRD AMENDMENT TO LOAN AGREEMENT AND OMNIBUS AMENDMENT (this
"Amendment") dated as of December 20, 2002 is among GIANT YORKTOWN, INC., a
Delaware corporation (the "Borrower"), GIANT INDUSTRIES, INC., a Delaware
corporation ("Giant Industries"), GIANT INDUSTRIES ARIZONA, INC., an Arizona
corporation ("Giant Arizona", and together with Giant Industries, the "Parent
Guarantors"), WELLS FARGO BANK NEVADA, NATIONAL ASSOCIATION, a national banking
association, not in its individual capacity (except as specifically set forth
herein), but solely in its capacity as collateral agent (the "Collateral
Agent"), and each of the Persons listed on the signature pages hereto as a
Lender (each, a "Lender").

                               R E C I T A L S:

         A.       The Borrower, the Collateral Agent and the Lenders have
heretofore entered into that certain Loan Agreement (as amended by that certain
Amendment to Loan Agreement and Omnibus Amendment dated as of May 22, 2002 (the
"First Amendment"), that certain Second Amendment to Loan Agreement and Omnibus
Amendment dated as of October 28, 2002 (the "Second Amendment"), and as further
amended, supplemented or otherwise modified from time to time, the "Loan
Agreement") dated as of May 14, 2002. Giant Industries and Giant Arizona have
heretofore entered into that certain Parent Guaranty Agreement (as amended by
the First Amendment, the Second Amendment, and as further amended, supplemented
or otherwise modified from time to time, the "Parent Guaranty") dated as of May
14, 2002. Capitalized terms used, but not otherwise defined in this Amendment,
shall have those meanings assigned to such terms in Section 1 to the Loan
Agreement, as amended hereby.

         B.       The parties hereto desire to amend the Loan Agreement and
certain of the other Operative Documents.

         C.       All requirements of law have been fully complied with and all
other acts and things necessary to make this Amendment a valid, legal and
binding instrument according to its terms for the purposes herein expressed have
been done or performed.

         NOW, THEREFORE, in consideration of good and valuable consideration the
receipt and sufficiency of which is hereby acknowledged, the parties hereto do
hereby agree as follows:

SECTION 1.        AMENDMENTS TO LOAN AGREEMENT.

         Section 1.1.  Section 1. (a) Section 1 of the Loan Agreement shall be
and is hereby amended by amending and restating in their entirety the following
definitions to read as follows:

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                  "Additional Collateral" shall mean the "Pledged Collateral"
         (as such term is defined in the Pledge Agreements) and the "Property"
         (as such term is defined in the Mortgages)."

                  ""Collateral" shall mean the Mortgaged Property and the
         Additional Collateral, together with all property and interests in
         property and proceeds thereof now owned or hereafter acquired by the
         Borrower or any Parent Guarantor and their respective Subsidiaries in
         or upon which a Lien now or hereafter exists in favor of the Lenders,
         or the Collateral Agent on behalf of the Lenders, whether under the
         Deed of Trust, the Pledge Agreements, the Mortgages, or under any other
         document executed by any such Person and delivered to the Collateral
         Agent or the Lenders."

                  ""Material Adverse Effect" shall mean (a) a material adverse
         change in, or a material adverse effect upon, the operations, business,
         properties, liabilities (actual or contingent), capitalization or
         condition (financial or otherwise) of Giant Industries and its
         Subsidiaries taken as a whole; (b) a material impairment of the ability
         of Borrower, Giant Industries or any Significant Subsidiary to perform
         under any Operative Document and to avoid any Event of Default; or (c)
         a material adverse effect upon (i) the legality, validity, binding
         effect or enforceability against Borrower, Giant Industries or any
         Significant Subsidiary of any Operative Document or any rights or
         remedies under any thereof, (ii) the perfection or priority of any Lien
         granted under any of the Operative Documents, (iii) the rights or
         interests of the Collateral Agent or any Lender in the Collateral or
         (iv) the Fair Market Value, use, utility, useful life or condition of
         the Mortgaged Property, other than any Partial Casualty pursuant to
         which the Borrower has paid the Partial Casualty Amount or is
         rebuilding the affected portion of the Mortgaged Property pursuant to
         SECTION 3.6."

                  ""Operative Documents" shall mean this Loan Agreement
         (including all Annexes, Exhibits and Schedules hereto), the Deed, the
         Parent Guaranty, the Constituent Companies Guaranty, the Deed of Trust,
         the Mortgages, the Pledge Agreements, the Bill of Sale, the Notes, the
         Fee Letters, the Engagement Letter, the Closing Notice, and any
         Assignment and Assumption and all other related agreements and
         documents issued or delivered hereunder or thereunder or pursuant
         hereto or thereto (in each case as the same may be amended, modified,
         restated, supplemented, extended, renewed or replaced from time to
         time), and "Operative Document" shall mean any one of them."

         (b)      Section 1 of the Loan Agreement shall be and is hereby further
amended by inserting in alphabetical order the following new defined terms:

                  ""Bloomfield Refinery" shall mean that certain oil refinery
         owned by Giant Four Corners located in McKinley County, New Mexico."

                  ""Ciniza Refinery" shall mean that certain oil refinery owned
         by San Juan Refining Company located in San Juan County, New Mexico."

                                      -2-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                  ""Giant Four Corners" shall mean Giant Four Corners, Inc., an
         Arizona corporation and a subsidiary of Giant Arizona."

                  ""Intercreditor Agreement" shall mean the Intercreditor
         Agreement dated as of December 20, 2002 between the Collateral Agent on
         behalf of the Lenders and the Administrative Agent on behalf of the
         Revolving Credit Lenders."

                  ""Mortgage" shall mean each Mortgage, Assignment of Rents and
         Leases, Security Agreement, Fixture Filing and Financing Statement
         dated as of December 20, 2002 from Giant Industries or any Subsidiary
         to the Collateral Agent, as secured party, for the benefit of the
         Lenders, and any other mortgage, deed of trust or similar document from
         Giant Industries or any Subsidiary to the Collateral Agent, granting a
         security interest in real property of Giant Industries or any
         Subsidiary."

                  ""Pledge Agreements" shall mean, collectively, (a) the Pledge
         Agreement dated as of December 20, 2002 from Giant Industries in favor
         of the Collateral Agent, as secured party, for the benefit of the
         Lenders, (b) the Pledge Agreement dated as of December 20, 2002 from
         Giant Arizona in favor of the Collateral Agent, as secured party, for
         the benefit of the Lenders and (c) the Pledge Agreement dated as of
         December 20, 2002 from Giant Four Corners in favor of the Collateral
         Agent, as secured party, for the benefit of the Lenders."

         Section 1.2.  Section 8.1. (a) Subparagraph (c) of Section 8.1 of the
Loan Agreement shall be and is hereby amended and restated in its entirety to
read as follows:

                  "(c)     Specific Defaults. Giant Industries, Giant Arizona,
         Borrower or any Subsidiary, as the case may be, (i) fails to perform or
         observe any term, covenant or agreement contained in (A) Section
         6(b)(i), 6(c)(i), 6(f), 6(n), 6(r), 6(t), 6(u), 6A(l), 6A(m), 6A(n),
         6A(o), 6A(s) or 6A(t) of the Parent Guaranty, (B) SECTION 3.2, 3.5, 3.7
         or SECTION 5 of this Loan Agreement, or (C) Section 2.1(b) or 2.1(n) of
         the Mortgages; or (ii) fails to perform or observe any term, covenant
         or agreement contained in Section 6A of the Parent Guaranty (which is
         not specified in the foregoing clause (c)(i)), and such default shall
         continue unremedied for a period of 15 days after the occurrence
         thereof; or"

         (b)      Subparagraph (p)(ii) of Section 8.1 of the Loan Agreement
shall be and is hereby amended and restated in its entirety to read as follows:

                  "(ii)    the Operative Documents shall for any reason (other
         than pursuant to the terms thereof) cease to create a valid security
         interest in the Collateral purported to be covered thereby or such
         security interest shall for any reason cease to be a perfected and
         first priority security interest; or"

         Section 1.3.  Section 8.2. Subparagraph (c) of Section 8.2 of the Loan
Agreement shall be and is hereby amended and restated in its entirety to read as
follows:

                                      -3-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                  "(c)     The Collateral Agent for the benefit of the Lenders
         may enforce any and all rights and remedies available to it under the
         Notes, the Deed of Trust, the Guaranties, the Pledge Agreements or the
         Mortgages or under any Requirement of Law."

         Section 1.4.  Section 8.3. Section 8.3 of the Loan Agreement shall be
and is hereby amended and restated in its entirety to read as follows:

                           "Section 8.3. Bankruptcy Defaults. If any Event of
         Default described in subsection (f) or (g) of SECTION 8.1 has occurred
         and is continuing, then the entire Loan Balance and all accrued and
         unpaid Interest thereon, and all fees, charges and other amounts
         payable hereunder, including, without limitation, any Applicable
         Administrative Charge, under the Notes, the Deed of Trust, the
         Guaranties, the Pledge Agreements and the Mortgages, shall immediately
         become due and payable without presentment, demand, protest or notice
         of any kind. In addition, the Collateral Agent at the direction of the
         Required Lenders may exercise any and all remedies available to it
         hereunder, under the Notes, the Deed of Trust, the Guaranties, the
         Pledge Agreements and the Mortgages or under any Requirement of Law."

         Section 1.5.  Section 9.1. Subparagraph (a) of Section 9.1 of the Loan
Agreement shall be and is hereby amended by deleting the phrase "Mortgaged
Property" where said phrase appears and substituting therefor the phrase
"Collateral."

         Section 1.6.  Section 9.2. Section 9.2 of the Loan Agreement shall be
and is hereby amended by deleting the phrase "Mortgaged Property" where said
phrase appears and substituting therefor the phrase "Collateral."

         Section 1.7.  Section 12.5. The introductory paragraph of Section 12.5
of the Loan Agreement shall be and is hereby amended and restated to read as
follows:

                           "Section 12.5. Effect and Modification. This Loan
         Agreement and the other Operative Documents exclusively and completely
         state the rights of the Lenders and Borrower with respect to the Loans
         and the Collateral and supersedes all prior agreements, oral or
         written, with respect thereto. No Operative Document nor any of the
         terms thereof may be terminated, amended, supplemented, waived or
         modified without the written agreement or consent of Collateral Agent,
         Borrower and the Required Lenders, and in the case of the Parent
         Guaranty, the Constituent Company Guaranty or any definition used
         therein, the Guarantors affected thereby, and in the case of any
         Mortgage or Pledge Agreement or any definition used therein, the entity
         which has delivered the same; provided, however, that SECTIONS 12.1 and
         12.16 hereof may not be terminated, amended, supplemented, waived or
         modified without the written agreement or consent of the Arranger; and
         provided, further, that any termination, amendment, supplement, waiver
         or modification shall require the written agreement or consent of each
         Lender if such termination, amendment, supplement, waiver or
         modification would:"

                                      -4-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

         Section 1.8.  Section 12.14. The penultimate sentence of Section 12.14
of the Loan Agreement shall be and is hereby amended by deleting the phrase
"Mortgaged Property" where said phrase appears and substituting therefor the
phrase "Collateral."

SECTION 2.        AMENDMENTS TO PARENT GUARANTY.

         Section 2.1.  Section 2. (a) Subparagraphs (A) and (F) and the third
grammatical paragraph of Section 2 of the Parent Guaranty shall be and is hereby
amended by deleting the phrase "Mortgaged Property" where said phrase appears
and substituting therefor the phrase "Collateral."

         Section 2.2.  Section 6. (a) Subparagraph (q) of Section 6 of the
Parent Guaranty shall be amended by deleting the phrase "Mortgaged Property"
where said phrase appears and substituting therefor the phrase "Collateral."

         Section 2.3.  Section 6A. Clause (i) of Subparagraph (a) of Section 6A
of the Parent Guaranty shall be and is hereby amended and restated in its
entirety to read as follows:

                           "(i)     (A) any Lien (other than a Lien on property
                  constituting Mortgaged Property) existing on property of Giant
                  Industries or any Subsidiary on the Closing Date and set forth
                  in SCHEDULE 6A(a) securing Indebtedness outstanding on such
                  date, (B) Liens on the Yorktown Assets described in SCHEDULE
                  6A(a) securing Borrower's obligations under the Loan Agreement
                  and (C) Liens on the Additional Collateral (but not on any
                  other Mortgaged Property) in favor of (1) the Collateral Agent
                  for the benefit of the Lenders and (2) the Revolving Credit
                  Lenders securing the "Obligations" under the Giant Industries
                  Credit Agreement, provided, that such Liens shall be subject
                  to the terms of an intercreditor agreement between the
                  Collateral Agent on behalf of the Lenders and the
                  Administrative Agent for the Revolving Credit Lenders, such
                  intercreditor agreement to be in form and substance
                  satisfactory to the Collateral Agent and the Required
                  Lenders."

SECTION 3.        REPRESENTATIONS AND WARRANTIES

         In order to induce the Collateral Agent and the Lenders to enter into
this Amendment, the Borrower and the Guarantors each represent and warrant to
the Collateral Agent and to each Lender that:

                  (a)      This Amendment, the Loan Agreement and the Parent
         Guaranty (each as amended hereby) and each other Operative Document
         have been duly authorized, executed and delivered by the Borrower and
         the Guarantors and constitute their legal, valid and binding
         obligations enforceable in accordance with their respective terms
         (subject, as to the enforcement of remedies, to applicable bankruptcy,
         reorganization, insolvency, moratorium and similar laws affecting
         creditors' rights generally and to general principles of equity).

                                      -5-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                  (b)      The representations and warranties set forth in
         Section 2 of the Loan Agreement and Section 5 of the Parent Guaranty
         are true and correct in all material respects on and as of the
         Amendment Effective Date, after giving effect to this Amendment, as if
         made on and as of the Amendment Effective Date.

                  (c)      The representations and warranties set forth in
         Section 5(x) of the Parent Guaranty which apply to the Mortgaged
         Property are true and correct in all material respects with respect to
         the Additional Collateral which constitutes real property on and as of
         the Amendment Effective Date.

                  (d)      As of the date hereof, at the time of and after
         giving effect to this Amendment, no Default or Event of Default (other
         than the Specified Defaults (as defined in the Second Amendment)) has
         occurred and is continuing.

                  (e)      Except as related to the Leay Acres landfill site
         located in San Juan County, NM, as described in Giant Industries' most
         recently filed Annual Report on Form 10-Q, no event or circumstance has
         occurred that has resulted or would reasonably be expected to result in
         a Material Adverse Effect.

                  (f)      No approval, consent, exemption, authorization or
         other action by, or notice to, or filing (other than filings required
         under Section 6(u) of the Parent Guaranty, as amended hereby) with, any
         Governmental Authority is necessary or required in connection with the
         execution and delivery of this Amendment or the performance by the
         Borrower or any Guarantor of its obligations hereunder and under the
         other Operative Documents. This Amendment and the other Operative
         Documents have been duly authorized by all necessary corporate action,
         and the execution, delivery and performance of this Amendment and the
         other Operative Documents and the documents and transactions
         contemplated hereby does not and will not (a) contravene the terms of
         the Borrower's or any Guarantor's Organization Documents; (b) conflict
         with or result in any breach or contravention of, or result in or
         require the imposition or creation of any Lien under, any document
         evidencing any material Contractual Obligation to which the Borrower or
         any Guarantor is a party or any order, injunction, writ or decree of
         any Governmental Authority to which the Borrower or any Guarantor is
         subject; or (c) violate any Requirement of Law.

SECTION 4.        EFFECTIVENESS.

         This Amendment shall become effective on December 20, 2002 (the
"Amendment Effective Date") upon the satisfaction of the following conditions
precedent:

                  (a)      Amendment. The Collateral Agent and the Lenders shall
         have received counterparts of this Amendment duly executed by Giant
         Industries, Giant Arizona, the Borrower, the Constituent Company
         Guarantors, the Collateral Agent, and the Required Lenders.

                                      -6-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                  (b)      Mortgages. The Collateral Agent and the Lenders shall
         have received duly executed Mortgages in form and substance
         satisfactory to the Required Lenders from Giant Industries, Giant
         Arizona and its Subsidiaries, as applicable, pursuant to which each
         such entity shall grant to the Collateral Agent, for the benefit of the
         Lenders, security interests in the real property assets referenced in
         the first paragraph of Section 6(u) of the Second Amendment.

                  (c)      Pledge Agreements. The Collateral Agent and the
         Lenders shall have received duly executed Pledge Agreements in form and
         substance satisfactory to the Required Lenders from each of Giant
         Industries, Giant Arizona and Giant Four Corners, pursuant to which
         each such entity shall grant to the Collateral Agent, for the benefit
         of the Lenders, security interests in the capital stock, partnership
         interests, and membership interests (as the case may be) of its
         Subsidiaries.

                  (d)      Intercreditor Agreement. The Collateral Agent and the
         Administrative Agent for the Revolving Credit Lenders shall have
         entered into an Intercreditor Agreement in form and substance
         satisfactory to the Required Lenders.

                  (e)      Stock Certificates. All certificates or instruments
         representing or evidencing the collateral pledged pursuant to the
         Pledge Agreements (together with stock powers executed in blank) shall
         have been delivered to the Collateral Agent or its designated agent or
         bailee, for the equal and ratable benefit of the Collateral Agent, the
         Lenders, the Administrative Agent and the Revolving Credit Lenders.

                  (f)      Filing and Recording. The Mortgages and Pledge
         Agreements (and/or financing statements or similar notices thereof if
         and to the extent permitted and required by applicable law) shall have
         been recorded or filed for record in all public offices as may be
         deemed necessary or appropriate by the Required Lenders or Lenders'
         special counsel in order to perfect the liens and security interests
         granted thereby.

                  (g)      No Default under, and Amendment of, Giant Industries
         Credit Agreement. Giant Industries shall have provided evidence
         satisfactory to the Collateral Agent and the Lenders that no default or
         event of default shall exist under the Giant Industries Credit
         Agreement.

                  (h)      Resolutions. The Collateral Agent and the Lenders
         shall have received (i) resolutions of the board of directors of the
         Parent Guarantors authorizing the execution and delivery of this
         Amendment and each Mortgage and Pledge Agreement to which it is a
         party, certified by the Secretary or an Assistant Secretary of each
         such entity; (ii) resolutions of the board of directors of the Borrower
         authorizing the execution and delivery of this Amendment, certified by
         its Secretary or an Assistant Secretary; (iii) resolutions of the board
         of directors of Giant Four Corners authorizing the execution and
         delivery of each Mortgage and Pledge Agreement to which it is a party,
         certified by its Secretary or an Assistant Secretary; and (iv)
         resolutions of the board of directors of any other Subsidiary of Giant
         Industries which shall execute and deliver a Mortgage,

                                      -7-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

         authorizing the execution and delivery of such Mortgage, certified by
         its Secretary or an Assistant Secretary.

                  (i)      Incumbency. The Collateral Agent and the Lenders
         shall have received a certificate of the Secretary or Assistant
         Secretary of the Parent Guarantors, the Borrower, Giant Four Corners
         and any Subsidiary which shall execute and deliver a Mortgage,
         certifying the names and true signatures of the officers of each such
         entity authorized to execute and deliver the relevant documents to
         which it is a party.

                  (j)      Opinions. The Collateral Agent and the Lenders shall
         have received the favorable opinions of (i) the General Counsel to the
         Guarantors and the Borrower with respect to the due authorization,
         execution and delivery of this Amendment and the Operative Documents,
         (ii) special New York counsel to the Guarantor and the Borrower with
         respect to the enforceability of this Amendment and the Operative
         Documents and (iii) special New Mexico counsel to the Guarantors with
         respect to the enforceability of the Mortgages, each such opinion to be
         in form and substance satisfactory to the Collateral Agent, the Lenders
         and their counsel and addressing such other matters as the Collateral
         Agent, the Lenders and their counsel may reasonably request.

                  (k)      No Material Adverse Effect. Except as disclosed in
         writing to the Collateral Agent and the Lenders prior to the Amendment
         Effective Date, no event or circumstance has occurred that has resulted
         or would reasonably be expected to result in a Material Adverse Effect.

                  (l)      No Default. As of the Amendment Effective Date, no
         Default or Event of Default (other than the Specified Defaults (as
         defined in the Second Amendment)) shall have occurred or be continuing.

                  (m)      Payment of Fees. Giant Industries shall have paid all
         accrued, unpaid fees, costs and expenses owed pursuant to this
         Amendment, the Operative Documents or any other agreement between the
         Parent Guarantors and the Borrower and the Collateral Agent or any
         Lender, to the extent then due and payable, together with Attorney
         Costs of the Collateral Agent to the extent then invoiced prior to or
         on the closing date of this Amendment.

                  (n)      Other. The Lenders shall have received such other
         approvals, opinions and documents as the Lenders deem appropriate.

Upon satisfaction of the foregoing conditions precedent set forth in this
Section 5, the Collateral Agent shall notify Giant Industries and the Lenders in
writing, and the date set forth in such notice shall be the effective date of
this Amendment.

SECTION 5.        COSTS, EXPENSES AND TAXES.

         Giant Industries agrees to pay on demand reasonable Attorney Costs of
the Lenders and the Collateral Agent and all other costs and expenses of the
Lenders and the Collateral Agent in

                                      -8-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

connection with the preparation, execution and delivery of this Amendment and
the mortgages, assignments, security agreements, financing statements and other
documents and instruments contemplated hereby. In addition, Giant Industries
shall pay any and all stamp and other taxes and fees payable or determined to be
payable in connection with the execution and delivery, filing or recording of
this Amendment and the other documents and instruments to be executed and
delivered hereunder, and agrees to save the Collateral Agent and the Lenders
harmless from and against any and all liabilities with respect to or resulting
from any delay in paying or omission to pay such taxes or fees.

SECTION 6.        MISCELLANEOUS.

         Section 6.1.  Guarantor Obligations. Each Guarantor hereby ratifies and
affirms in all respects it obligations under its guaranty and acknowledges that
such guaranty shall remain in full force and effect.

         Section 6.2.  Construction. This Amendment shall be construed in
connection with and as part of the Loan Agreement and the other Operative
Documents, and except as modified and expressly amended by this Amendment, all
terms, conditions and covenants contained in the Loan Agreement and the other
Operative Documents are hereby ratified and shall be and remain in full force
and effect.

         Section 6.3.  Headings and Table of Contents. The headings of the
Sections of this Amendment are inserted for purposes of convenience only and
shall not be construed to affect the meaning or construction of any of the
provisions hereof and any reference to numbered Sections, unless otherwise
indicated, are to Sections of this Amendment.

         Section 6.4.  References. Any and all notices, requests, certificates
and other instruments executed and delivered after the execution and delivery of
this Amendment may refer to the Loan Agreement and the other Operative Documents
without making specific reference to this Amendment but nevertheless all such
references shall be deemed to include this Amendment unless the context
otherwise requires.

         Section 6.5.  Counterparts. This Amendment may be executed in any
number of counterparts, each executed counterpart constituting an original but
all together only one Amendment.

         Section 6.6.  Governing Law. This Amendment shall be governed by and
construed in accordance under the laws of the State of New York without regard
to conflict of law principles (other than Title 14 of Article V of the New York
General Obligation Law).

                      [Signature Pages begin on Next Page]

                                      -9-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

          Executed and delivered as of this 20th day of December, 2002.

                            GIANT YORKTOWN, INC., as Borrower

                            By:        /s/ GARY R. DALKE
                               -------------------------------------------------
                                Name:  Gary R. Dalke
                                Its: VP, Controller and Chief Accounting Officer

                            GIANT INDUSTRIES, INC., as a Guarantor

                            By:        /s/ GARY R. DALKE
                               -------------------------------------------------
                                Name:  Gary R. Dalke
                                Its: VP, Controller and Chief Accounting Officer

                            GIANT INDUSTRIES ARIZONA, INC. , as a Guarantor

                            By:        /s/ GARY R. DALKE
                               -------------------------------------------------
                                Name:  Gary R. Dalke
                                Its: VP, Controller and Chief Accounting Officer

                                      -10-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            BLACK DIAMOND INTERNATIONAL FUNDING, LTD., as a
                              Lender

                            By:        /s/ ALAN CORKISH
                               -------------------------------------------------
                                Name:  Alan Corkish
                                Title: Director

                                      -11-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            TRS1 LLC, as a Lender

                            By:        /s/ Rosemary F. Dunne
                               -------------------------------------------------
                                Name:  Rosemary F. Dunne
                                Title: Attorney-in-Fact

                                      -12-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            GMAC BUSINESS CREDIT LLC, as a Lender

                            By:        /s/ L. M. STEVENS
                               -------------------------------------------------
                                Name:  L. M. Stevens
                                Title: Division Chief Credit Officer

                                      -13-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            ORIX FINANCIAL SERVICES, INC., as a Lender

                            By:        /s/ MARK A. KASSIS
                               -------------------------------------------------
                                Name:  Mark A. Kassis
                                Title: Senior Vice President

                                      -14-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            TRANSAMERICA EQUIPMENT FINANCIAL SERVICES
                              CORPORATION, as a Lender

                            By:        /s/ JAMES R. BATES
                               -------------------------------------------------
                                Name:  James R. Bates
                                Title: Vice President

                                      -15-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            WELLS FARGO BANK NEVADA, NATIONAL ASSOCIATION, as
                              Collateral Agent

                            By:        /s/ C. SCOTT NIELSEN
                               -------------------------------------------------
                                Name:  C. Scott Nielsen
                                Title: Trust Officer

                                      -16-

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

         Each of the undersigned hereby acknowledges and agrees to the terms of
the foregoing Amendment and further confirms its continued guaranty of the
obligations of the Borrower under the Loan Agreement, as amended hereby,
pursuant to the terms of its guaranty on this 20th day of December, 2002.

                            GIANT FOUR CORNERS, INC.

                            By         /s/ GARY R. DALKE
                              --------------------------------------------------
                                Name:  Gary R. Dalke
                                Title: VP, Controller and Chief Accounting
                                       Officer
                                Address: c/o Giant Industries, Inc.
                                         23733 North Scottsdale Road
                                         Scottsdale, Arizona 85255-3465
                                         Attention: President

                            SAN JUAN REFINING COMPANY

                            By         /s/ GARY R. DALKE
                              --------------------------------------------------
                                Name:  Gary R. Dalke
                                Title: VP, Controller and Chief Accounting
                                       Officer
                                Address: c/o Giant Industries, Inc.
                                         23733 North Scottsdale Road
                                         Scottsdale, Arizona 85255-3465
                                         Attention: President

                            PHOENIX FUEL CO., INC.

                            By         /s/ GARY R. DALKE
                              --------------------------------------------------
                                Name:  Gary R. Dalke
                                Title: VP, Controller and Chief Accounting
                                       Officer
                                Address: c/o Giant Industries, Inc.
                                         23733 North Scottsdale Road
                                         Scottsdale, Arizona 85255-3465
                                         Attention: President

                                      -17

<PAGE>

Giant Yorktown, Inc.                           Third Amendment to Loan Agreement

                            GIANT MID-CONTINENT, INC.

                            By         /s/ GARY R. DALKE
                              --------------------------------------------------
                                Name:  Gary R. Dalke
                                Title: VP, Controller and Chief Accounting
                                       Officer
                                Address: c/o Giant Industries, Inc.
                                         23733 North Scottsdale Road
                                         Scottsdale, Arizona 85255-3465
                                         Attention: President

                            GIANT STOP-N-GO OF NEW MEXICO, INC.

                            By         /s/ GARY R. DALKE
                              --------------------------------------------------
                                Name:  Gary R. Dalke
                                Title: VP, Controller and Chief Accounting
                                       Officer
                                Address: c/o Giant Industries, Inc.
                                         23733 North Scottsdale Road
                                         Scottsdale, Arizona 85255-3465
                                         Attention: President

                                      -18-