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                                                                    EXHIBIT 10.4

                               GUARANTY AGREEMENT

      This Guaranty Agreement dated as of July 13, 2004 (this "Guaranty") is
executed by each of the undersigned (individually a "Guarantor" and
collectively, the "Guarantors"), in favor of Union Bank of California, N.A, as
Administrative Agent for the ratable benefit of itself, the Banks (as defined
below), the Issuing Banks (as defined below), and the Swap Counterparties (as
defined below) (together with the Administrative Agent, the Issuing Banks, the
Banks, individually a "Beneficiary", and collectively, the "Beneficiaries").

                                  INTRODUCTION

      A. This Guaranty is given in connection with that certain Credit Agreement
dated as of July 7, 2004 (as it has been or may be amended, supplemented or
otherwise modified from time to time, the "Credit Agreement"), among HEP
Operating Company, L.P., a Delaware limited partnership (the "Borrower"), the
Banks party thereto from time to time (individually, a "Bank", and collectively
the "Banks"), the Banks issuing letters of credit thereunder from time to time
(individually, an "Issuing Bank", and collectively, the "Issuing Banks") and
Union Bank of California, N.A. as an administrative agent (the "Administrative
Agent") for such Banks and Issuing Banks.

      B. Each Guarantor is a Subsidiary of the Borrower and will derive
substantial direct and indirect benefit from (i) the transactions contemplated
by the Credit Agreement and the other Credit Documents and (ii) the Interest
Rate Contracts entered into by the Borrower or any of its Subsidiaries with a
Bank or an Affiliate of a Bank (each such counterparty being referred to as a
"Swap Counterparty").

      C. Each Guarantor is executing and delivering this Guaranty (i) to induce
the Banks to provide Advances under the Credit Agreement, (ii) to induce the
Issuing Banks to provide Letters of Credit under the Credit Agreement, and (iii)
intending it to be a legal, valid, binding, enforceable and continuing
obligation of such Guarantor, whether or not such Guarantor derives any benefit
from the Credit Agreement or from any other Credit Document.

      NOW, THEREFORE, in consideration of the premises, each Guarantor hereby
agrees as follows:

      Section 1. Definitions. All capitalized terms not otherwise defined in
this Guaranty that are defined in the Credit Agreement shall have the meanings
assigned to such terms by the Credit Agreement.

      Section 2. Guaranty.

(a) Each Guarantor hereby absolutely, unconditionally and irrevocably guarantees
the punctual payment and performance, when due, whether at stated maturity, by
acceleration or otherwise, of all Obligations, whether absolute or contingent
and whether for principal, interest (including, without limitation, interest
that but for the existence of a bankruptcy, reorganization or similar proceeding
would accrue), fees, amounts owing in respect of Letter of Credit Obligations,
amounts required to be provided as collateral, indemnities, expenses or
otherwise (collectively, the "Guaranteed Obligations"). Without limiting the
generality of the foregoing,

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each Guarantor's liability shall extend to all amounts that constitute part of
the Guaranteed Obligations and would be owed by the Borrower to the
Administrative Agent, any Issuing Bank or any Bank under the Credit Documents
and by the Borrower to any Swap Counterparty but for the fact that they are
unenforceable or not allowable due to insolvency or the existence of a
bankruptcy, reorganization or similar proceeding involving the Borrower.

(b) It is the intention of the Guarantors and each Beneficiary that the amount
of the Guaranteed Obligations guaranteed by each Guarantor shall be in, but not
in excess of, the maximum amount permitted by fraudulent conveyance, fraudulent
transfer or similar Legal Requirements applicable to such Guarantor.
Accordingly, notwithstanding anything to the contrary contained in this Guaranty
or in any other agreement or instrument executed in connection with the payment
of any of the Guaranteed Obligations, the amount of the Guaranteed Obligations
guaranteed by a Guarantor under this Guaranty shall be limited to an aggregate
amount equal to the largest amount that would not render such Guarantor's
obligations hereunder subject to avoidance under Section 548 of the United
States Bankruptcy Code or any comparable provision of any other applicable law.

      Section 3. Guaranty Absolute. Each Guarantor guarantees that the
Guaranteed Obligations will be paid strictly in accordance with the terms of the
Credit Documents, regardless of any law, regulation or order now or hereafter in
effect in any jurisdiction affecting any of such terms or the rights of the
Administrative Agent, any Issuing Bank, any Bank or any Swap Counterparty with
respect thereto but subject to Section 2(b) above. The obligations of each
Guarantor under this Guaranty are independent of the Guaranteed Obligations or
any other obligations of any other Person under the Credit Documents or in
connection with any Interest Rate Contract, and a separate action or actions may
be brought and prosecuted against any Guarantor to enforce this Guaranty,
irrespective of whether any action is brought against the Borrower, any other
Guarantor or any other Person or whether the Borrower, any other Guarantor or
any other Person is joined in any such action or actions. The liability of each
Guarantor under this Guaranty shall be irrevocable, absolute and unconditional
irrespective of, and each Guarantor hereby irrevocably waives any defenses it
may now or hereafter have in any way relating to, any or all of the following:

(a) any lack of validity or enforceability of any Credit Document or any
agreement or instrument relating thereto or any part of the Guaranteed
Obligations being irrecoverable;

(b) any change in the time, manner or place of payment of, or in any other term
of, all or any of the Guaranteed Obligations or any other obligations of any
Person under the Credit Documents or any agreement or instrument relating to
Interest Rate Contract with a Swap Counterparty, or any other amendment or
waiver of or any consent to departure from any Credit Document or any agreement
or instrument relating to Interest Rate Contract with a Swap Counterparty,
including, without limitation, any increase in the Guaranteed Obligations
resulting from the extension of additional credit to the Borrower or otherwise;

(c) any taking, exchange, release or non-perfection of any collateral, or any
taking, release or amendment or waiver of or consent to departure from any other
guaranty, for all or any of the Guaranteed Obligations;

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(d) any manner of application of collateral, or proceeds thereof, to all or any
of the Guaranteed Obligations, or any manner of sale or other disposition of any
collateral for all or any of the Guaranteed Obligations or any other obligations
of any other Person under the Credit Documents or any other assets of the
Borrower or any of its Subsidiaries;

(e) any change, restructuring or termination of the corporate structure or
existence of the Borrower or any of its Subsidiaries;

(f) any failure of any Bank, the Administrative Agent, any Issuing Bank or any
other Beneficiary to disclose to the Borrower or any Guarantor any information
relating to the business, condition (financial or otherwise), operations,
properties or prospects of any Person now or in the future known to the
Administrative Agent, any Issuing Bank, any Bank or any other Beneficiary (and
each Guarantor hereby irrevocably waives any duty on the part of any Beneficiary
to disclose such information);

(g) any signature of any officer of the Borrower being mechanically reproduced
in facsimile or otherwise; or

(h) any other circumstance or any existence of or reliance on any representation
by any Beneficiary that might otherwise constitute a defense available to, or a
discharge of, the Borrower, any Guarantor or any other guarantor, surety or
other Person.

      Section 4. Continuation and Reinstatement, Etc. Each Guarantor agrees
that, to the extent that payments of any of the Guaranteed Obligations are made,
or any Bank, the Administrative Agent, any Issuing Bank or any Swap Counterparty
receives any proceeds of collateral, and such payments or proceeds or any part
thereof are subsequently invalidated, declared to be fraudulent or preferential,
set aside, or otherwise required to be repaid, then to the extent of such
repayment the Guaranteed Obligations shall be reinstated and continued in full
force and effect as of the date such initial payment or collection of proceeds
occurred. EACH GUARANTOR SHALL DEFEND AND INDEMNIFY EACH BENEFICIARY FROM AND
AGAINST ANY CLAIM, DAMAGE, LOSS, LIABILITY, COST OR EXPENSE UNDER THIS SECTION 4
(INCLUDING REASONABLE ATTORNEYS' FEES AND EXPENSES) IN THE DEFENSE OF ANY SUCH
ACTION OR SUIT INCLUDING SUCH CLAIM, DAMAGE, LOSS, LIABILITY, COST, OR EXPENSE
ARISING AS A RESULT OF THE INDEMNIFIED BENEFICIARY'S OWN NEGLIGENCE BUT
EXCLUDING SUCH CLAIM, DAMAGE, LOSS, LIABILITY, COST, OR EXPENSE THAT IS FOUND IN
A FINAL, NON-APPEALABLE JUDGMENT BY A COURT OF COMPETENT JURISDICTION TO HAVE
RESULTED FROM SUCH INDEMNIFIED BENEFICIARY'S GROSS NEGLIGENCE OR WILLFUL
MISCONDUCT.

      Section 5. Waivers and Acknowledgments.

(a) Each Guarantor hereby waives promptness, diligence, presentment, notice of
acceptance and any other notice with respect to any of the Guaranteed
Obligations and this Guaranty and any requirement that any Beneficiary protect,
secure, perfect or insure any Lien or any property or exhaust any right or take
any action against the Borrower or any other Person or any collateral.

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(b) Each Guarantor hereby irrevocably waives any right to revoke this Guaranty,
and acknowledges that this Guaranty is continuing in nature and applies to all
Guaranteed Obligations, whether existing now or in the future.

(c) Each Guarantor acknowledges that it will receive substantial direct and
indirect benefits from the financing arrangements involving the Borrower
contemplated by the Credit Documents and the Interest Rate Contracts with the
Swap Counterparties and that the waivers set forth in this Guaranty are
knowingly made in contemplation of such benefits.

      Section 6. Subrogation. No Guarantor will exercise any rights that it may
now have or hereafter acquire against the Borrower or any other Person to the
extent that such rights arise from the existence, payment, performance or
enforcement of such Guarantor's obligations under this Guaranty or any other
Credit Document, including, without limitation, any right of subrogation,
reimbursement, exoneration, contribution or indemnification and any right to
participate in any claim or remedy of any Beneficiary against the Borrower or
any other Person, whether or not such claim, remedy or right arises in equity or
under contract, statute or common law, including, without limitation, the right
to take or receive from the Borrower or any other Person, directly or
indirectly, in cash or other property or by set-off or in any other manner,
payment or security on account of such claim, remedy or right, unless and until
all of the Guaranteed Obligations and any and all other amounts payable by the
Guarantors under this Guaranty shall have been paid in full in cash, all Letters
of Credit have terminated or expired and no Letter of Credit Obligations shall
remain outstanding, and all Commitments shall have expired or terminated. If any
amount shall be paid to a Guarantor in violation of the preceding sentence at
any time prior to (a) the payment in full in cash of the Guaranteed Obligations
and any and all other amounts payable by the Guarantors under this Guaranty, (b)
the satisfaction of all Letter of Credit Obligations and the termination of all
obligations of the Issuing Banks and the Banks in respect of Letters of Credit,
and (c) the termination of the Commitments, such amount shall be held in trust
for the benefit of the Beneficiaries and shall forthwith be paid to the
Administrative Agent to be credited and applied to the Guaranteed Obligations
and any and all other amounts payable by the Guarantors under this Guaranty,
whether matured or unmatured, in accordance with the terms of the Credit
Documents.

      Section 7. Representations and Warranties. Each Guarantor hereby
represents and warrants as follows:

(a) There are no conditions precedent to the effectiveness of this Guaranty.
Such Guarantor benefits from executing this Guaranty.

(b) Such Guarantor has, independently and without reliance upon the
Administrative Agent, the Issuing Bank or any Bank and based on such documents
and information as it has deemed appropriate, made its own credit analysis and
decision to enter into this Guaranty, and such Guarantor has established
adequate means of obtaining from the Borrower and each other relevant Person on
a continuing basis information pertaining to, and is now and on a continuing
basis will be reasonably familiar with, the business, condition (financial and
otherwise), operations, properties and prospects of the Borrower and each other
relevant Person.

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(c) The obligations of such Guarantor under this Guaranty are the valid, binding
and legally enforceable obligations of such Guarantor, and the execution and
delivery of this Guaranty by such Guarantor has been duly and validly authorized
in all respects by such Guarantor, and the Person who is executing and
delivering this Guaranty on behalf of such Guarantor has full power, authority
and legal right to so do, and to observe and perform all of the terms and
conditions of this Guaranty on such Guarantor's part to be observed or
performed.

      Section 8. Right of Set-Off. Upon the occurrence and during the
continuance of any Event of Default, any Bank or the Administrative Agent, the
Issuing Bank and any other Beneficiary is hereby authorized at any time, to the
fullest extent permitted by law, to set off and apply any deposits (general or
special, time or demand, provisional or final) and other indebtedness owing by
such Beneficiary to the account of each Guarantor against any and all of the
obligations of the Guarantors under this Guaranty, irrespective of whether or
not such Beneficiary shall have made any demand under this Guaranty and although
such obligations may be contingent and unmatured. Such Beneficiary shall
promptly notify the affected Guarantor after any such set-off and application is
made, provided that the failure to give such notice shall not affect the
validity of such set-off and application. The rights of the Beneficiaries under
this Section 8 are in addition to other rights and remedies (including, without
limitation, other rights of set-off) which any Beneficiary may have.

      Section 9. Amendments, Etc. No amendment or waiver of any provision of
this Guaranty and no consent to any departure by any Guarantor therefrom shall
in any event be effective unless the same shall be in writing and signed by the
affected Guarantor, the Administrative Agent and the Majority Banks, and then
such waiver or consent shall be effective only in the specific instance and for
the specific purpose for which given; provided that no amendment, waiver or
consent shall, unless in writing and signed by all of the Banks, (a) other than
to the extent expressly provided in such amendment, waiver or consent, limit the
liability of any Guarantor hereunder (it being understood that waivers and
amendments permitted to be made under the Credit Agreement by the Majority Banks
with respect to any of the underlying obligations guaranteed hereunder shall not
be deemed to limit the liability of any Guarantor within the meaning of this
clause (a)), (b) postpone any date fixed for payment hereunder in respect of any
of the Guaranteed Obligations that is principal of, or interest on, the Notes or
any fees, or Letter of Credit Obligations, or (c) change the percentage of the
Commitments or of the aggregate unpaid principal amount of the Notes required to
take any action hereunder.

      Section 10. Notices, Etc. All notices and other communications provided
for hereunder shall be sent in the manner provided for in Section 9.02 of the
Credit Agreement and if to a Guarantor, at its address specified on the
signature page hereto and if to the Administrative Agent, any Issuing Bank or
any Bank, at its address specified in or pursuant to the Credit Agreement, and
if to a Swap Counterparty, at its address specified in the applicable Interest
Rate Contract. All such notices and communications shall be effective when
delivered, except that notices and communications to the Administrative Agent
shall not be effective until received by the Administrative Agent.

      Section 11. No Waiver: Remedies. No failure on the part of the
Administrative Agent or any other Beneficiary to exercise, and no delay in
exercising, any right hereunder shall operate as a waiver thereof; nor shall any
single or partial exercise of any right hereunder preclude any

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other or further exercise thereof or the exercise of any other right. The
remedies herein provided are cumulative and not exclusive of any remedies
provided by law.

      Section 12. Continuing Guaranty: Assignments under the Credit Agreement.
This Guaranty is a continuing guaranty and shall (a) remain in full force and
effect until the payment in full of all Guaranteed Obligations and all other
amounts payable under the Credit Documents, the termination of all Letter of
Credit Obligations, and the termination of all the Commitments, (b) be binding
upon each Guarantor and its successors and assigns, (c) inure to the benefit of
and be enforceable by the Administrative Agent, each Bank, and each Issuing
Bank, and their respective successors, and, in the case of transfers and
assignments made in accordance with the Credit Agreement, transferees and
assigns, and (d) inure to the benefit of and be enforceable by a Swap
Counterparty and each of its successors, transferees and assigns to the extent
such successor, transferee or assign is a Bank or an Affiliate of a Bank.
Without limiting the generality of the foregoing clause (c), subject to Section
9.06 of the Credit Agreement, any Bank may assign or otherwise transfer all or
any portion of its rights and obligations under the Credit Agreement (including,
without limitation, all or any portion of its Commitment, the Advances owing to
it and the Note or Notes held by it) to any other Person, and such other Person
shall thereupon become vested with all the benefits in respect thereof granted
to such Bank herein or otherwise, subject, however, in all respects to the
provisions of the Credit Agreement. Each Guarantor acknowledges that upon any
Person becoming a Bank, the Administrative Agent, or an Issuing Bank in
accordance with the Credit Agreement, such Person shall be entitled to the
benefits hereof.

      Section 13. Governing Law. This Guaranty shall be governed by, and
construed and enforced in accordance with, the laws of the State of Texas. Each
Guarantor hereby irrevocably submits to the jurisdiction of any Texas state or
federal court sitting in Dallas, Texas in any action or proceeding arising out
of or relating to this Guaranty and the other Credit Documents, and each
Guarantor hereby irrevocably agrees that all claims in respect of such action or
proceeding may be heard and determined in such court. Each Guarantor hereby
irrevocably waives, to the fullest extent it may effectively do so, any right it
may have to the defense of an inconvenient forum to the maintenance of such
action or proceeding. Each Guarantor hereby agrees that service of copies of the
summons and complaint and any other process which may be served in any such
action or proceeding may be made by mailing or delivering a copy of such process
to such Guarantor at its address set forth in the Credit Agreement or set forth
on the signature page of this Guaranty. Each Guarantor agrees that a final
judgment in any such action or proceeding shall be conclusive and may be
enforced in other jurisdictions by suit on the judgment or in any other manner
provided by law. Nothing in this Section shall affect the rights of any
Beneficiary to serve legal process in any other manner permitted by the law or
affect the right of any Beneficiary to bring any action or proceeding against
any Guarantor or its Property in the courts of any other jurisdiction.

      Section 14. INDEMNIFICATION. EACH GUARANTOR SHALL INDEMNIFY EACH OF THE
BENEFICIARIES, AND THEIR RESPECTIVE DIRECTORS, OFFICERS, EMPLOYEES AND AGENTS
FROM, AND DISCHARGE, RELEASE, AND HOLD EACH OF THEM HARMLESS AGAINST, ANY AND
ALL LIABILITIES, OBLIGATIONS, LOSSES, CLAIMS, EXPENSES, OR DAMAGES OF ANY KIND
OR NATURE WHATSOEVER TO WHICH ANY OF THEM MAY BECOME SUBJECT

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RELATING TO OR ARISING OUT OF THIS GUARANTY, INCLUDING ANY LIABILITIES,
OBLIGATIONS, LOSSES, CLAIMS, EXPENSES, OR DAMAGES WHICH ARISE OUT OF OR RESULT
FROM (A) ANY ACTUAL OR PROPOSED USE BY THE BORROWER, ANY GUARANTOR OR ANY
AFFILIATE OF THE BORROWER OR ANY GUARANTOR OF THE PROCEEDS OF THE ADVANCES, (B)
ANY BREACH BY THE BORROWER OR ANY GUARANTOR OF ANY PROVISION OF THE CREDIT
AGREEMENT OR ANY OTHER CREDIT DOCUMENT, (C) ANY INVESTIGATION, LITIGATION OR
OTHER PROCEEDING (INCLUDING ANY THREATENED INVESTIGATION OR PROCEEDING) RELATING
TO THE FOREGOING, (D) ANY ENVIRONMENTAL CLAIM OR REQUIREMENT OF ENVIRONMENTAL
LAWS CONCERNING OR RELATING TO THE PRESENT OR PREVIOUSLY-OWNED OR OPERATED
PROPERTIES OF THE BORROWER, ANY GUARANTOR OR THE OPERATIONS OR BUSINESS, OF THE
BORROWER OR ANY GUARANTOR, OR (E) ANY ENVIRONMENTAL CLAIM OR REQUIREMENT OF
ENVIRONMENTAL LAWS CONCERNING OR RELATED TO THE BORROWER'S OR ANY GUARANTOR'S
PROPERTIES AND EACH GUARANTOR SHALL REIMBURSE THE BENEFICIARIES AND THEIR
RESPECTIVE DIRECTORS, OFFICERS, EMPLOYEES AND AGENTS, UPON DEMAND FOR ANY
REASONABLE OUT-OF-POCKET EXPENSES (INCLUDING REASONABLE OUTSIDE LEGAL FEES)
INCURRED IN CONNECTION WITH ANY SUCH INVESTIGATION, LITIGATION OR OTHER
PROCEEDING; AND EXPRESSLY INCLUDING ANY SUCH LOSSES, LIABILITIES, CLAIMS,
DAMAGES, OR EXPENSE INCURRED BY REASON OF THE PERSON BEING INDEMNIFIED'S OWN
NEGLIGENCE, BUT EXCLUDING ANY SUCH LOSSES, LIABILITIES, CLAIMS, DAMAGES OR
EXPENSES THAT IS FOUND IN A FINAL, NON-APPEALABLE JUDGMENT BY A COURT OF
COMPETENT JURISDICTION TO HAVE RESULTED FROM SUCH INDEMNIFIED PERSON'S GROSS
NEGLIGENCE OR WILLFUL MISCONDUCT.

      Section 15. WAIVER OF JURY TRIAL. EACH GUARANTOR HEREBY ACKNOWLEDGES THAT
IT HAS BEEN REPRESENTED BY AND HAS CONSULTED WITH COUNSEL OF ITS CHOICE, AND
HEREBY KNOWINGLY, VOLUNTARILY, INTENTIONALLY, AND IRREVOCABLY WAIVES ANY AND ALL
RIGHT TO TRIAL BY JURY IN RESPECT OF ANY LEGAL PROCEEDING ARISING OUT OF OR
RELATING TO THIS GUARANTY, ANY OTHER CREDIT DOCUMENT, OR ANY OF THE TRANSACTIONS
CONTEMPLATED HEREBY OR THEREBY.

      Section 16. Additional Guarantors. Pursuant to Section 5.10 of the Credit
Agreement, each Subsidiary of the Borrower (other than a Restricted Subsidiary)
that was not in existence on the date of the Credit Agreement is required to
enter into this Guaranty as a Guarantor upon becoming a Subsidiary. Upon
execution and delivery after the date hereof by the Administrative Agent and
such Subsidiary of an instrument in the form of Annex 1, such Subsidiary shall
become a Guarantor hereunder with the same force and effect as if originally
named as a Guarantor herein. The execution and delivery of any instrument adding
an additional Guarantor as a party to this Guaranty shall not require the
consent of any other Guarantor hereunder. The rights and obligations of each
Guarantor hereunder shall remain in full force and effect notwithstanding the
addition of any new Guarantor as a party to this Guaranty.

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      Section 17. ORAL AGREEMENTS. PURSUANT TO SECTION 26.02 OF THE TEXAS
BUSINESS AND COMMERCE CODE, AN AGREEMENT IN WHICH THE AMOUNT INVOLVED IN
AGREEMENT EXCEEDS $50,000 IN VALUE IS NOT ENFORCEABLE UNLESS THE AGREEMENT IS IN
WRITING AND SIGNED BY THE PARTY TO BE BOUND OR THAT PARTY'S AUTHORIZED
REPRESENTATIVE.

      THE RIGHTS AND OBLIGATIONS OF THE PARTIES TO AN AGREEMENT SUBJECT TO THE
PRECEDING PARAGRAPH SHALL BE DETERMINED SOLELY FROM THE WRITTEN AGREEMENT, AND
ANY PRIOR ORAL AGREEMENTS BETWEEN THE PARTIES ARE SUPERSEDED BY AND MERGED INTO
THIS GUARANTY. THIS GUARANTY AND THE CREDIT DOCUMENTS REPRESENT THE FINAL
AGREEMENT AMONG THE PARTIES WITH RESPECT TO THE SUBJECT MATTER HEREOF AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES.

      THERE ARE NO UNWRITTEN ORAL AGREEMENTS AMONG THE PARTIES.

               [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK.]

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      Each Guarantor has caused this Guaranty to be duly executed as of the date
first above written.

                         GUARANTORS:

                         HEP PIPELINE GP, L.L.C., a Delaware
                                  limited liability company
                         HEP REFINING GP, L.L.C., a Delaware
                                  limited liability company
                         HEP MOUNTAIN HOME, L.L.C., a Delaware
                                  limited liability company
                         HEP PIPELINE, L.L.C., a Delaware
                                  limited liability company
                         HEP REFINING, L.L.C., a Delaware
                                  limited liability company
                         HEP WOODS CROSS, L.L.C., a Delaware
                                  limited liability company

                         Each by: HEP Operating Company, L.P., a Delaware
                                  limited partnership and its Sole Member

                              By: HEP Logistics GP, L.L.C., a Delaware limited
                                  liability company, its General Partner

                              By: Holly Energy Partners, L.P., a Delaware
                                  limited partnership, its Managing Member

                              By: HEP Logistics Holdings, L.P., a Delaware
                                  limited partnership, its General Partner

                              By: Holly Logistic Services, L.L.C., a Delaware
                                  limited liability company, its General Partner

                                  By: /s/ M. Neale Hickerson
                                      ----------------------------------------
                                           M. Neale Hickerson
                                           Vice President - Treasury and
                                           Investor Relations

                               Address of Guarantors:
                               100 Crescent Court, Suite 1600
                               Dallas, Texas  75201-6927
                               Facsimile: (214) 871-3850
                               Attention: Steve McDonnell

                           [Signature pages continue.]

                      Signature page to Guaranty Agreement

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                         HEP NAVAJO SOUTHERN, L.P., a Delaware limited
                              partnership
                         HEP PIPELINE ASSETS, LIMITED PARTNERSHIP,
                              a Delaware limited partnership

                         Each by: HEP Pipeline GP, L.L.C., a Delaware limited
                                  liability company and its General Partner

                              By: HEP Operating Company, L.P., a Delaware
                                  limited partnership and its Sole Member

                              By: HEP Logistics GP, L.L.C., a Delaware limited
                                  liability company, its General Partner

                              By: Holly Energy Partners, L.P., a Delaware
                                  limited partnership, its Managing Member

                              By: HEP Logistics Holdings, L.P., a Delaware
                                  limited partnership, its General Partner

                             By: Holly Logistic Services, L.L.C.,
                                 a Delaware limited liability company,
                                 its General Partner

                                       By: /s/ M. Neale Hickerson
                                           -----------------------------------
                                            M. Neale Hickerson
                                            Vice President - Treasury and
                                            Investor Relations

                              Address of Guarantors:
                              100 Crescent Court, Suite 1600
                              Dallas, Texas  75201-6927
                              Facsimile: (214) 871-3850
                              Attention: Steve McDonnell

                           [Signature pages continue.]

                      Signature page to Guaranty Agreement

<PAGE>

                         HEP REFINING ASSETS, L.P., a Delaware limited
                                  partnership

                              By: HEP Refining GP, L.L.C., a Delaware limited
                                  liability company and its General Partner

                              By: HEP Operating Company, L.P., a Delaware
                                  limited partnership and its Sole Member

                              By: HEP Logistics GP, L.L.C., a Delaware limited
                                  liability company, its General Partner

                              By: Holly Energy Partners, L.P., a Delaware
                                  limited partnership,its Managing Member

                              By: HEP Logistics Holdings, L.P., a Delaware
                                  limited partnership, its General Partner

                              By: Holly Logistic Services, L.L.C., a Delaware
                                  limited liability company, its General Partner

                                  By: /s/ M. Neale Hickerson
                                      ----------------------------------------
                                       M. Neale Hickerson
                                       Vice President - Treasury and
                                       Investor Relations

                               Address of Guarantor:
                               100 Crescent Court, Suite 1600
                               Dallas, Texas  75201-6927
                               Facsimile: (214) 871-3850
                               Attention: Steve McDonnell

                      Signature page to Guaranty Agreement