FIFTH AMENDMENT TO GUARANTY


     This Amendment, dated as of September 8, 1995, is entered into by
(1) FRONTIER OIL CORPORATION, a Delaware corporation (the
"Guarantor"), (2) the banks (the "Banks") parties to the Credit
Agreement (as hereinafter defined) and (3) UNION BANK, a California
banking corporation, as agent (the "Agent") for the Banks.

Recitals

     A.   Frontier oil and Refining Company, a Delaware corporation
(the "Borrower"), the Banks and the Agent have entered into a
Revolving Credit and Letter of Credit Agreement dated as of August 10,
1992, as amended by a letter of waiver and amendment dated March 17,
1993, a Second Amendment to Revolving Credit and Letter of Credit
Agreement dated as of April 30, 1993, a Third Amendment to Revolving
Credit and Letter of Credit Agreement dated as of December 31, 1993, a
Fourth Amendment to Revolving Credit and Letter of Credit Agreement
dated as of July 6, 1994 and a Fifth Amendment to Revolving Credit and
Letter of Credit Agreement dated as of July 1, 1995 (said Agreement,
as so amended, herein called the "Credit Agreement").  Terms defined
in the credit Agreement and not otherwise defined herein have the same
respective meanings when used herein, and the rules of interpretation
set forth in Sections 1.2 and 1.3 of the Credit Agreement are
incorporated herein by reference.

     B.   The Guarantor has executed a Guaranty dated as of August 18,
1992, as amended by a First Amendment to Guaranty dated as of October
8, 1992, a letter of waiver and amendment dated March 17, 1993, a
Second Amendment to Guaranty dated as of December 31, 1993, a Third
Amendment to Guaranty dated July 6, 1994 and a Fourth Amendment to
Guaranty dated July 1, 1995 (said Guaranty, as so amended, herein
called the "Guaranty"), in favor of the Banks and the Agent,
guaranteeing all of the obligations of the Borrower under the Credit
Agreement and the other Credit Documents.

     C.   The Guarantor, the Banks and the Agent wish to (1) amend the
Guaranty to change the terms of certain of the covenants contained
therein and (2) take action to permit (a) the Guarantor to contribute
to Frontier Pipeline, Inc. ("FPLI") the shares of Frontier Products,
Inc. ("FPI") owned by the Guarantor and (b) the subsequent merger of
FPI into FPLI.  Accordingly, the Guarantor, the Banks and the Agent
hereby agree as set forth below.

     Section 1.   Amendments to Guaranty.  Effective as of the date
hereof and subject to satisfaction of the conditions precedent set
forth in Section 2, the Guaranty is hereby amended as follows:

          (a)  Section 7.2(b)(v) of the Guaranty is amended in full to
read as follows:

               "(v) Debt to brokerage firms listed on Schedule 3, or
to Wainoco in respect of Debt of Wainoco (incurred on behalf of the
Guarantor or any of its Subsidiaries in the purchase or sale of
commodity futures contracts or related options) to brokerage firms
listed on Schedule 3, all such Debt not to exceed three million five
hundred thousand dollars ($3,500,000) for the Guarantor and its
Subsidiaries in the aggregate at any time, relating to commodity
hedging activity in margin accounts, but only to the extent that such
activity is permitted pursuant to Section 7.2(g)."

          (b)  Section 7.2(f)(vii) of the Guaranty is amended in full
to read as follows:


               "(vii) the Guarantor or any of its Subsidiaries from
making the following payments:  (A) payments from time to time to
Wainoco equal to the Guarantor's or such Subsidiary's liability to
Wainoco pursuant to the Guarantor's and its Subsidiaries' tax-sharing
arrangement with Wainoco; provided, however, that such payments shall
not exceed the Guarantor's or such Subsidiary's current tax liability
that would otherwise by payable to the Internal Revenue Service or
other appropriate Governmental Persons if the Guarantor or such
Subsidiary were required to pay taxes on an unconsolidated, stand-
alone basis; or (B) payments from time to time to Wainoco in respect
of Debt of the Guarantor or such Subsidiary to Wainoco permitted
pursuant to Section 7.2(b)(v)."

          (c)   Section 7.2(g) of the Guaranty is amended in full to
read as follows:

          "(g)  Commodity Futures Contracts.  The Guarantor will not
purchase or sell, or permit any of its Subsidiaries to purchase or
sell, either by purchasing or selling directly or by purchasing or
selling indirectly through Wainoco or any other Person acting on
behalf of the Guarantor or such Subsidiary, (i) any 'hedged' (as
defined pursuant to generally accepted accounting principles)
commodity futures contracts or related options, except such contracts
or related options that are (A) for the sale or purchase of crude oil
or petroleum products and are traded on the New York Mercantile

                                 - 2 -

Exchange, (B) entered into in the ordinary course of the business of
the Guarantor or such Subsidiary, (C) economically appropriate and
consistent with such business, (D) used to offset price risks
incidental to cash or spot transactions in crude oil or petroleum
products, (E) established and liquidated in accordance with sound
commercial practices and (F) held by a broker listed on Schedule 3; or
(ii) any unhedged commodity futures contracts or related options,
except contracts or related options that are (A) for the sale or
purchase of crude oil or petroleum products and are traded on the New
York Mercantile Exchange, (B) held by a broker listed on Schedule 3
and (C) not in excess of one hundred (100) contracts in the aggregate
at any one time."


          (d)  Schedule 3 to the Guaranty is amended by deleting the
first entry thereon and substituting the following:

               "Smith Barney
                Galleria Financial Center
                5065 Westheimer, Suite 900
                Houston, Texas 77056".

     Section 2.  Conditions to Effectiveness.  This Amendment shall
become effective when the Agent has received all of the following
documents, each dated the date hereof, in form and substance
satisfactory to the Agent and in the number of originals requested by
the Agent:

          (a)   this Amendment executed by the Guarantor and the
Banks;

          (b)   a consent to this Amendment duly executed by Wainoco
and the Guarantors other than Frontier Oil Corporation; and

          (c)   such other approvals, opinions and documents as the
Agent may reasonably request.

     Section 3. Representations and Warranties of Guarantor.  The
Guarantor represents and warrants as follows:

          (a)   The Guarantor is a corporation duly organized, validly
existing and in good standing under the laws of the State of Delaware.

          (b)   The execution, delivery and performance by the
Guarantor of this Amendment and the Credit Documents, as amended
hereby, to which it is or is to be a party are within the Guarantor's
corporate powers, have been duly authorized by all necessary corporate
action and do not (i) contravene the Guarantor's charter documents or
bylaws, (ii) contravene any

                                 - 3 -

Governmental Rule or contractual restriction binding on or affecting the
Guarantor or (iii) result in or require the creation or imposition of any
Lien or preferential arrangement of any nature (other than any created by
the Credit Documents) upon or with respect to any of the properties now
owned or hereafter acquired by the Guarantor.

          (c)   No Governmental Action is required for the due
execution, delivery and performance by the Guarantor of this Amendment
or any of the Credit Documents, as amended hereby, to which the
Guarantor is or is to be a party.

          (d)   This Amendment and each of the Credit Documents, as
amended hereby, to which the Guarantor is a party constitute legal,
valid and binding obligations of the Guarantor enforceable against the
Guarantor in accordance with their respective terms.

          (d)   The Stock Pledge Agreement constitutes a valid and
perfected a first-priority Lien on the Collateral covered thereby,
enforceable against all third parties in all jurisdictions, and
secures the payment of all obligations of the Guarantor under the
Guaranty, as amended hereby; and the execution, delivery and
performance of this Amendment do not adversely affect the Lien of the
Stock Pledge Agreement.

          (f)   The consolidated balance sheet of the Guarantor and
its Subsidiaries as of December 31, 1994 and the related consolidated
statements of income, retained earnings and cash flows of the
Guarantor and its Subsidiaries for the fiscal year then ended,
certified by Arthur Andersen & Co., independent public accountants,
and the report as of July 31, 1995 referred to in Section 7.1(j) (i)
of the Guaranty, certified by the chief financial officer or chief
accounting officer of the Guarantor, fairly present the consolidated
financial condition of the Guarantor and its Subsidiaries as of such
dates and the consolidated results of the operations of the Guarantor
and its Subsidiaries for the fiscal periods ended on such dates, all
in accordance with generally accepted accounting principles applied on
a consistent basis.  Since July 31, 1995 there has been no material
adverse change in the business, condition (financial or otherwise),
operations, performance, properties or prospects of the Guarantor or
any of its Subsidiaries.  The Guarantor and its Subsidiaries have no
material contingent liabilities except as disclosed in such financial
statements or the notes thereto.

          (g)   There is no pending or, to the knowledge of the
Guarantor, threatened action or proceeding affecting the Guarantor or
any its Subsidiaries before any Governmental Person or arbitrator that
may materially and adversely affect the financial condition or
operations of the Guarantor or any of its Subsidiaries or that
purports to affect the legality, validity or enforceability of this
Amendment or any of the Credit Documents, as amended hereby, to which
the Guarantor is a party.

                                 - 4 -

          (h)   The representations and warranties contained in the
Credit Documents are true in all material respects as though made on
and as of the effective date of this Amendment.

          (i)   No event has occurred and is continuing, or would
result from the effectiveness of this Amendment, that constitutes a
Default or an Event of default.

     Section 4.  Consent and Waiver.  Effective as of the date hereof
and subject to satisfaction of the conditions precedent set forth in
Section 2, the Banks hereby consent to (a) the Guarantor's
contribution to FPLI of the shares of FPI held by the Guarantor and
(b) the subsequent merger of FPI into FPLI, and the Banks hereby waive
any requirements of the Credit Document that would otherwise prohibit
that contribution or merger.

     Section 5.  Reference to and Effect on credit Documents.

          (a)   On and after the effective date of this Amendment,
each reference in the Guaranty to "this Guaranty," "hereunder,"
"hereof," "herein" or any other expression of like import referring to
the Guaranty, and each reference in the other Credit Documents to "the
FOC guaranty," "thereunder," "thereof," "therein" or any other
expression of like import referring to the Guaranty, shall mean and be
a reference to the Guaranty as amended by this Amendment.

          (b)   Except as specifically amended or waived above, the
Guaranty and the other Credit Documents shall remain in full force and
effect and are hereby ratified and confirmed.  Without limiting the
generality of the foregoing, the Stock Pledge Agreement and all of the
Collateral described therein do and shall continue to secure the
payment of all obligations of the Guarantor under the Guaranty, as
amended hereby.

          (c)   The execution, delivery and effectiveness of this
Amendment shall not, except as expressly provided herein, operate as a
waiver of any right, power or remedy of any Bank or the Agent under
any of the Credit Documents or constitute a waiver of any provision of
any of the Credit Documents.

     Section 6.  Costs, Expenses and Taxes.  The Guarantor agrees to
pay on demand all costs and expenses of the Agent in connection with
the preparation, execution and delivery of this Amendment and the
other instruments and documents to be delivered hereunder, including
the reasonable fees and out-of-pocket expenses of counsel for the
Agent with respect thereto and with respect to advising the Agent as
to its rights and responsibilities hereunder and thereunder.  In
addition, the Guarantor shall pay any and all stamp and other taxes
payable or determined to be payable in connection with the execution
and delivery of this Amendment and the other instruments and documents
to be delivered

                                 - 5 -

hereunder, and the Guarantor agrees to save the Agent and each Bank
harmless from and against any and all liabilities with respect to or
resulting from any delay in paying or omission to pay such taxes.

     Section 7.  Execution in Counterparts.  This Amendment may be
executed in any number of counterparts and by the parties hereto in
separate counterparts, each of which when so executed and delivered
shall be deemed to be an original and all of which taken together
shall constitute one and the same instrument.

     Section 8.  Governing Law.  THIS AMENDMENT SHALL BE GOVERNED BY,
AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF CALIFORNIA
APPLICABLE TO CONTRACTS MADE AND PERFORMED IN THE STATE OF CALIFORNIA.


FRONTIER OIL CORPORATION


By:  /s/  John D. Galvin
     ----------------------------
     Jon D. Galvin
     Vice President and Chief Financial Officer


UNION BANK, as Agent and as a Bank


By:  /s/  Richard P. DeGrey, Jr.
     ----------------------------
     Richard P. DeGrey, Jr.
     Vice President

                                 - 6 -


BANQUE PARIBAS


By:  /s/  Mark M. Green
     ----------------------------
Name:  Mark M. Green
Title:  Vice President


By:  /s/ Barton D. Schouest
     ----------------------------
Name:  Barton D. Schouest
Title:  Group Vice President


DEN NORSKE BANK AS


By:  /s/ Alfred C. Jones, III*
     ---------------------------
Name:  Alfred C. Jones, III
Title:  Senior Vice President and General Counsel


By:  /s/ Fran Meyer
     ---------------------------
Name:  Fran Meyer
Title:  Vice President

                                 - 7 -


CONSENT

     Effective as of September 8, 1995, (1) WAINOCO OIL CORPORATION,
as obligor under the Support and Clawback Agreement made as of August
18, 1992 (the "Support Agreement") in favor of the Banks (as defined
in the Credit Agreement referred to below) and Union Bank, as agent
(the "Agent") for the Banks, and (2) each of FRONTIER HOLDINGS INC.,
FRONTIER REFINING INC. and FRONTIER PIPELINE INC., as guarantor under
its respective Guaranty dated as of August 18, 1992 in favor of the
Banks and the Agent, hereby consent to the Fifth Amendment to Guaranty
substantially in the form attached hereto as Exhibit A (the "Guaranty
Amendment") and hereby confirm and agree that the Support Agreement or
such Guaranty, as applicable, is and shall continue to be in full
force and effect and is ratified and confirmed in all respects, except
that, on and after the effective date of the Guaranty Amendment, each
reference in the Support Agreement or such Guaranty to "the FOC
Guaranty," "thereunder," "thereof," "therein" or any other expression
of like import referring to the FOC Guaranty (as defined in the Credit
Agreement referred to in the Guaranty Amendment) shall mean and be a
reference to the FOC Guaranty as amended by the Guaranty Amendment.


WAINOCO OIL CORPORATION


By:  /s/ Julie H. Edwards
     ---------------------------
     Julie H. Edwards
     Senior Vice President - Finance
       and Chief Financial Officer and Treasurer


FRONTIER HOLDINGS INC.


By:  /s/ Jon D. Galvin
     ---------------------------
     Jon D. Galvin
     Vice President and
       Chief Financial Officer


FRONTIER REFINING INC.


By:  /s/ Jon D. Galvin
     ---------------------------
     Jon D. Galvin
     Vice President and
       Chief Financial Officer


FRONTIER PIPELINE INC.


By:  /s/ Jon D. Galvin
     ---------------------------
     Jon D. Galvin
     Vice President

                                 - 2 -