FIRST AMENDMENT TO MORTGAGE, DEED OF TRUST, ASSIGNMENT
           OF PRODUCTION, SECURITY AGREEMENT AND FINANCING STATEMENT


     THIS FIRST AMENDMENT TO MORTGAGE,  DEED OF TRUST, ASSIGNMENT OF PRODUCTION,
SECURITY AGREEMENT AND FINANCING STATEMENT (this "Amendment") is entered into as
of the effective time and date hereinafter stated (the "Effective Date") by  and
between TESORO E&P COMPANY, L.P., a Delaware limited partnership with an address
for   notice   hereunder   of  8700  Tesoro  Drive,  San  Antonio,  Texas  78217
("Mortgagor") and BANQUE PARIBAS, as Administrative Agent for the benefit of the
Issuing Banks and the Lenders, with  offices and banking quarters at 1200 Smith,
Suite 3100, Houston, Texas 77002 ("Mortgagee").  Any capitalized term  used  but
not  defined  in  this Amendment shall have the meaning assigned to such term in
the hereinafter described Credit Agreement.


                                R E C I T A L S


     A.   Tesoro Petroleum  Corporation  (the  "Company"),  Texas  Commerce Bank
National Association, as agent and various lenders (the "Prior Lenders") entered
into a Credit Agreement dated as of April 20, 1994  (as  amended  from  time  to
time,  the  "Prior  Credit  Agreement"), and Mortgagor and others entered into a
Guaranty Agreement dated  of  even  date  therewith  guaranteeing the prompt and
complete payment of the indebtedness and obligations of the  Company  under  the
Prior Credit Agreement (the "Prior Guaranty Agreement").

     B.   The  Prior  Credit  Agreement  and  the  Prior  Guaranty Agreement was
secured by, among other things, that certain Mortgage, Deed of Trust, Assignment
of Production, Security Agreement and Financing  Statement dated as of even date
therewith from Tesoro Exploration and Production Company ("TEP") to  Stephen  H.
Field,  as  Trustee  for  Texas Commerce Bank National Association, as agent, as
Mortgagee  ("Prior  Mortgagee")  for  the  benefit  of  the  Prior  Lenders (the
"Mortgage").

     C.   The Mortgage was duly recorded in Starr County,  Texas  on  April  25,
1994  in  Volume  692,  Page  523  of  the Official Public Records and in Zapata
County, Texas on April 15, 1994 in Volume 497, Page 340 of the Official Records.

     D.   TEP subsequently assigned all of its  right, title and interest in the
Mortgaged Property, as defined in the Mortgage, to Mortgagor.

     E.   Of even date herewith, the Company, Banque Paribas, as  Administrative
Agent,  The Bank of Nova Scotia, as Documentation Agent and various lenders (the
"Lenders") are entering  into  an  Amended  and  Restated  Credit Agreement (the
"Credit Agreement") amending


and restating the Prior Credit Agreement and carrying forward  the  indebtedness
thereunder,  and  Mortgagor and others are entering into an Amended and Restated
Guaranty Agreement amending and restating the Prior Guaranty Agreement.

     F.   Also of  even  date  herewith,  Prior  Mortgagee  is  entering into an
Assignment of Liens assigning all of its right, title  and  interest  under  the
Mortgage  to  Banque  Paribas,  as  Administrative  Agent for the benefit of the
Issuing Banks and the Lenders ("Mortgagee").

     G.   Mortgagor and Mortgagee now desire to amend the Mortgage.

     NOW, THEREFORE, in view of the foregoing, Mortgagor and Mortgagee do hereby
agree as follows:

     1.   All capitalized terms  used  but  not  defined  herein  shall have the
meanings assigned to such terms in the Mortgage.

     2.   All references in the Mortgage  to  "this  Mortgage",  as  defined  in
Section  1.02  of  the Mortgage shall mean the Mortgage as amended hereby and as
the same may from time to time be further amended or supplemented.

     3.   All references in the  Mortgage  to  "Mortgagor" shall mean Tesoro E&P
Company, L.P.; all references in the Mortgage to "Mortgagee" shall  mean  Banque
Paribas,  as  Administrative  Agent for the benefit of the Issuing Banks and the
Lenders; and all references in the Mortgage to "Credit Agreement" shall mean the
above-described Credit Agreement as  the  same  may  be amended, supplemented or
restated from time to time.

     4.   Section 1.03 of the Mortgage is amended in its entirety  to  hereafter
read as follows:

          "Section  1.03  Indebtedness  Secured.   This Mortgage is executed and
     delivered  by  Mortgagor  to   secure   and   enforce  the  following  (the
     "Indebtedness"):

          (a)  Payment  of  and  performance  of  any  and   all   indebtedness,
     obligations  and  liabilities of Mortgagor pursuant to that certain Amended
     and  Restated  Guaranty  Agreement  dated  June  7,  1996  executed  by the
     Mortgagor, among others, in favor  of  BANQUE  PARIBAS,  as  Administrative
     Agent  for  the Issuing Banks and the Lenders (as the same may from time to
     time  be  amended,  supplemented   or  otherwise  modified,  the  "Guaranty
     Agreement"), guaranteeing the prompt and complete payment when due (whether
     at the stated maturity, by acceleration or otherwise)  of  the  Obligations
     (as  defined  in the Guaranty Agreement) including, without limitation, the
     Letters of Credit and the Notes with  final maturity on or before April 30,
     2000 and any obligations arising under  the  Hedging  Agreements  with  any
     Lender or its Affiliates.

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          (b)  Any sums which may be advanced or paid by Mortgagee or any Lender
     under  the  terms  hereof  on account of the failure of Mortgagor to comply
     with the covenants  of  the  Mortgagor  contained  herein  or in the Credit
     Agreement; and all other indebtedness of Mortgagor arising pursuant to  the
     provisions of this Mortgage."

     5.   Mortgagor  hereby  confirms that it has heretofore granted, bargained,
sold, assigned, mortgaged, warranted,  transferred  and  conveyed to Trustee for
the benefit of Mortgagee, and granted a security interest to Mortgagee  in,  the
Mortgaged  Property,  and  Mortgagor  further  grants, bargains, sells, assigns,
mortgages, warrants,  transfers  and  conveys  to  Trustee  for  the  benefit of
Mortgagee, and grants  a  security  interest  to  Mortgagee  in,  the  Mortgaged
Property,  to  Mortgagee  on  behalf  of  the  Lenders to secure the payment and
performance of the Indebtedness as defined herein.

     6.   Mortgagor  hereby  confirms  that  it  has  heretofore  absolutely and
unconditionally assigned, transferred and conveyed and  does  hereby  absolutely
and unconditionally assign, transfer and convey to Mortgagee, its successors and
assigns,  all  of  the  Hydrocarbons  and  all  products  obtained  or processed
therefrom, and the revenues and  proceeds  now and hereafter attributable to the
Hydrocarbons and said products and all payments in lieu of the Hydrocarbons such
as "take or pay" payments or settlements.

     7.   The parties  hereto  hereby  acknowledge  and  agree  that  except  as
specifically  amended,  changed or modified hereby, the Mortgage shall remain in
full force and effect in accordance with  its terms.  None of the rights, titles
and interests existing and to exist under  the  Mortgage  are  hereby  released,
diminished   or   impaired,   and  Mortgagor  hereby  reaffirms  all  covenants,
representations and warranties made in the Mortgage.

     8.   This Amendment may be  executed  in  two  or more counterparts, and it
shall not be necessary that the signatures of all parties hereto be contained on
any one counterpart hereof.

                                      -3-

     EXECUTED the ___ day of June, 1996, to be effective as of the  7th  day  of
June, 1996 (the "Effective Date").

                              MORTGAGOR:

                              TESORO E&P COMPANY, L.P.

                              By:  Tesoro Exploration and Production Company,
                                   its general partner



                                   By: /s/ G. A. Wright
                                   Name:     G. A. Wright
                                   Title:    Vice President and Treasurer


                              MORTGAGEE:

                              BANQUE PARIBAS, AS ADMINISTRATIVE AGENT



                              By: /s/ Brian Malone
                              Name:     Brian Malone
                              Title:    Vice President



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

                                      -4-

STATE OF TEXAS

COUNTY OF HARRIS

     The  foregoing  instrument  was acknowledged before me the 7th day of June,
1996 by G. A. Wright,  Vice  President  and  Treasurer of TESORO EXPLORATION AND
PRODUCTION COMPANY, a Delaware corporation, on behalf of such corporation.


Seal:                         /s/ Linda Daugherty
                              Notary Public in and for the
                              State of Texas


STATE OF TEXAS

COUNTY OF HARRIS

     The foregoing instrument was acknowledged before me the 7th  day  of  June,
1996  by  Brian Malone, Vice President of BANQUE PARIBAS, a bank organized under
the laws of France, acting through its  Houston, Texas agency, on behalf of such
bank.


                              /s/ Linda Daugherty
Seal:                         Notary Public in and for the
                              State of Texas

STATE OF TEXAS

COUNTY OF HARRIS

     The foregoing instrument was acknowledged before me the 7th  day  of  June,
1996  by  Barton  D.  Schouest,  Group  Vice President of BANQUE PARIBAS, a bank
organized under the laws of France, acting through its Houston, Texas agency, on
behalf of such bank.


Seal:                         /s/ Linda Daugherty
                              Notary Public in and for the
                              State of Texas

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