<PAGE>   1
                                                                     EXHIBIT 4.1



                AMENDED AND RESTATED FIRST AMENDMENT AND CONSENT


         AMENDED AND RESTATED FIRST AMENDMENT AND CONSENT, dated as of November
10, 1999 (this "Amendment"), to the THIRD AMENDED AND RESTATED CREDIT AGREEMENT,
dated as of July 2, 1998, among TESORO PETROLEUM CORPORATION, a Delaware
corporation (the "Borrower"), the several banks and other financial institutions
or entities from time to time parties to thereto (the "Lenders"), LEHMAN
BROTHERS INC. ("LBI"), as advisor and arranger thereunder (in such capacity, the
"Arranger"), LEHMAN COMMERCIAL PAPER INC. ("LCPI"), as syndication agent
thereunder (in such capacity, the "Syndication Agent"), PARIBAS and BANK ONE, NA
(formerly known as The First National Bank of Chicago), as co-administrative
agents thereunder (in such capacity, the "Co-Administrative Agents"), BANK ONE,
NA (formerly known as The First National Bank of Chicago), as general
administrative agent thereunder (in such capacity, the "General Administrative
Agent"), PARIBAS, as collateral agent thereunder (in such capacity, the
"Collateral Agent"), and THE BANK OF NOVA SCOTIA, as documentation agent
thereunder (in such capacity, the "Documentation Agent").


                              W I T N E S S E T H:

         WHEREAS, pursuant to the Credit Agreement, the Lenders have agreed to
make, and have made, certain loans and other extensions of credit to the
Borrower;

         WHEREAS, the Borrower intends to sell, in two or more transactions, all
of the issued and outstanding Capital Stock of its subsidiaries and affiliates
engaged in the business of exploring and developing hydrocarbons, including
Tesoro Hydrocarbons Company USA, Tesoro Exploration and Production Company,
Tesoro E&P, L.P., Tesoro Reserves Company, Tesoro Gathering Company, Tesoro
Natural Gas Company and Tesoro Pipeline Company, L.P. (collectively, the
Domestic E&P Entities"; the sale of such entities, the "Domestic E&P Sale") and
Tesoro Bolivia Petroleum Company and Tesoro Latin American Company
(collectively, the "Bolivian E&P Entities"; the sale of such entities, the
"Bolivian E&P Sale"), and has requested the Lenders to consent thereto;

         WHEREAS, the Domestic E&P Sale and the Bolivian E&P Sale (collectively,
the "Sale") will require the release of all of the Domestic E&P Entities and the
Bolivian E&P Entities as Subsidiary Guarantors under the Guarantee and
Collateral Agreement, the release of all security interests in the Capital Stock
and assets of the Domestic E&P Entities and the Bolivian E&P Entities under the
Guarantee and Collateral Agreement, and the release of all of the Oil and Gas
Mortgages;

         WHEREAS, the Sale could be interpreted as a Fundamental Change under
the Credit Agreement;

         WHEREAS, pursuant to the First Amendment and Consent, dated as of
October 1, 1999 (the "Existing Amendment"), the Lenders consented to the Sale
upon the terms and conditions set forth therein;



<PAGE>   2

         WHEREAS, the Borrower has advised the Lenders that, as permitted (upon
Borrower providing the required Reinvestment Notice) by the Credit Agreement as
in effect prior to the effectiveness of the Existing Amendment, the Borrower may
wish to apply all or a portion of the proceeds of the Domestic E&P Sale toward
the acquisition of other assets useful in the business of the Borrower and its
Subsidiaries, and, to effect such acquisition as a like kind exchange pursuant
to applicable law, the Borrower wishes to deposit the portion of such proceeds
to be used for such acquisition in an escrow account (the "Escrow Account")
pending such application;

         WHEREAS, the agreements governing the Escrow Account will provide that
(i) the Borrower may withdraw funds from the Escrow Account during the six month
period following the consummation of the Domestic E&P Sale for application
toward the acquisition of assets useful in the business of the Borrower and its
Subsidiaries and qualifying for "like kind exchange" under applicable law, (ii)
the Borrower may at any time withdraw funds from the Escrow Account and apply
such proceeds toward prepayment of the Term Loans and (iii) any funds on deposit
in the Escrow Account on the date which is six months after the date of
consummation of the Domestic E&P Sale will be transferred to the General
Administrative Agent for application toward prepayment of the Term Loans, and
any such funds remaining after such prepayment will be transferred to the
Borrower;

         WHEREAS, in order to reflect the matters described in the preceding
recitals, the parties hereto wish to amend and restate the Existing Amendment in
its entirety;

         NOW, THEREFORE, in consideration of the premises and mutual agreements
contained herein, and for other valuable consideration the receipt of which is
hereby acknowledged, the Borrower and the Lenders hereby agree that on the
Amendment Effective Date (as defined in Section 4 below) the Existing Amendment
will be amended and restated in its entirety as follows:

         Definitions. Capitalized terms used herein and not otherwise defined
shall have the meanings assigned to such terms in the Credit Agreement.

      2. Consent. Subject to the terms and conditions hereof, the Lenders hereby
(a) consent to the Sale subject to the proceeds of the Sale being applied toward
the prepayment of the Term Loans and all accrued and unpaid interest thereon,
provided that all or any portion of the proceeds of the Domestic E&P Sale may be
deposited in the Escrow Account; and (b) authorize the Collateral Agent (i) to
release its security interest in all Capital Stock of, and property owned by,
the Domestic E&P Entities in connection with the Domestic E&P Sale (including,
without limitation, the Oil and Gas Mortgages), (ii) to release its security
interest in the Capital Stock of the Bolivian E&P Entities in connection with
the Bolivian E&P Sale and (iii) to release from its obligations under the
Guarantee and Collateral Agreement any Domestic E&P Entity and any Bolivian E&P
Entity whose Capital Stock is sold pursuant to the Sale.

      3. Amendments to Credit Agreement. (a) Section 1.1. of the Credit
Agreement is hereby amended by deleting the definitions of "Excluded
Subsidiaries" and "Responsible Officer" therefrom in their entirety and
substituting therefor the following:

            "Excluded Subsidiaries": the collective reference to the "Excluded
      Subsidiaries" listed on Schedule 4.15 attached hereto.



<PAGE>   3

            "Responsible Officer": the chief executive officer, president, chief
      financial officer, general counsel, executive vice president corporate
      resources, senior vice president financial resources, vice president
      finance, vice president controller, or vice president treasurer of the
      Borrower, but in any event, with respect to financial matters, the chief
      financial officer, controller, senior vice president financial resources,
      vice president finance, or vice president treasurer of the Borrower.

      (b) Schedule 4.15 of the Credit Agreement is hereby amended by deleting
such Schedule in its entirety and substituting in lieu thereof Schedule 4.15 in
Exhibit A attached hereto.

      (c) Section 7.7(g) of the Credit Agreement is hereby amended by deleting
such Section in its entirety and substituting in lieu thereof the following:

            "(g) to hold a 50% limited partnership interest in Tesoro Building
      Project, Ltd., a Delaware limited partnership."

      4. Conditions to Effectiveness. This Amendment shall become effective, as
of the date first written above, on the date (the "Amendment Effective Date") of
receipt by the General Administrative Agent of (i) counterparts of this
Amendment duly executed by the Borrower and the Required Lenders, and (ii)
counterparts of the Acknowledgment and Consent attached hereto executed by each
Subsidiary of the Borrower.

      5. Representations and Warranties. On and as of the date hereof, and after
giving effect to this Amendment, the Borrower confirms, reaffirms and restates
that the representations and warranties set forth in Section 4 of the Credit
Agreement are true and correct in all material respects, provided that the
references to the Credit Agreement therein shall be deemed to be references to
the Credit Agreement as amended by this Amendment.

      6. Limited Amendment. Except as expressly amended hereby, the Credit
Agreement is, and shall remain, in full force and effect. This Amendment shall
not be deemed to be a waiver of, or consent to, or a modification or amendment
of, any other term or condition of the Credit Agreement or to prejudice any
other right or rights which the Lenders may now have or may have in the future
under or in connection with the Credit Agreement or any of the instruments or
agreements referred to therein, as the same may be amended from time to time.

      7. Counterparts. This Amendment may be executed by one or more of the
parties hereto in any number of separate counterparts and all of said
counterparts taken together shall be deemed to constitute one and the same
instrument.


      8. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.


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      IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed and delivered by their respective duly authorized officers as of the
date first above written.



                                 TESORO PETROLEUM CORPORATION


                                 By:     /s/ SHARON L. LAYMAN
                                       ----------------------------------
                                 Name:   Sharon L. Layman
                                  Title: Vice President, Treasurer


                                 LEHMAN BROTHERS INC.,
                                   as Arranger


                                 By:     /s/ MICHELE SWANSON
                                       ----------------------------------
SYNDICATED LOAN FUNDING TRUST    Name:   Michele Swanson
BY: LEHMAN COMMERCIAL PAPER       Title: Authorized Signatory
INC. NOT IN ITS INDIVIDUAL
CAPACITY BUT SOLELY AS ASSET
MANAGER                          LEHMAN COMMERCIAL PAPER INC.,
                                   as Syndication Agent and as a Lender
/s/ MICHELE SWANSON
-----------------------------
Name:   Michele Swanson          By:     /s/ MICHELE SWANSON
Title:  Authorized Signatory           ----------------------------------
                                 Name:   Michele Swanson
                                  Title: Authorized Signatory


                                 BANK ONE, NA (formerly known as The
                                   First National Bank of Chicago), as Co-
                                   Administrative Agent, General Administrative
                                   Agent and as a Lender


                                 By:     /s/ THOMAS E. BOTH
                                       ----------------------------------
                                 Name:   Thomas E. Both
                                  Title: First Vice President


<PAGE>   5
                                 PARIBAS,
                                   as Co-Administrative Agent, Collateral
                                   Agent and as a Lender


                                 By:      /s/ BRIAN M. MALONE
                                    ----------------------------------
                                  Name:   Brian M. Malone
                                   Title: Director


                                 By:      /s/ BETSY JOCHER
                                    ----------------------------------
                                  Name:    Betsy Jocher
                                   Title:  Vice President


                                 THE BANK OF NOVA SCOTIA,
                                   as Documentation Agent and as a Lender


                                 By:      /s/ F.C.H. ASHBY
                                    ----------------------------------
                                  Name:   F.C.H. Ashby
                                   Title: Senior Manager Loan Operations


                                 ABN AMRO BANK N.V.


                                 By:      /s/ ALLEN V. POOLE
                                    ----------------------------------
                                  Name:   Allen V. Poole
                                   Title: Senior Vice President

                                 By:      /s/ W. BRYAN CHAPMAN
                                    ----------------------------------
                                  Name:   W. Bryan Chapman
                                   Title: Group Vice President

                                 BANK LEUMI USA

                                 By:      /s/ JOUNG HEE HONG
                                    ----------------------------------
                                  Name:   Joung Hee Hong
                                   Title: Vice President

                                 BANK OF HAWAII


                                 By:      /s/ BRENDA K. TESTERMAN
                                    ----------------------------------
                                  Name:   Brenda Testerman
                                   Title: Vice President



<PAGE>   6
                                BANK OF SCOTLAND


                                By:        /s/ ANNIE GLYNN
                                   ----------------------------------
                                 Name:     Annie Glynn
                                  Title:   Senior Vice President


                                THE BANK OF TOKYO-MITSUBISHI, LTD.


                                By:      /s/ JOHN MCGHEE
                                   ----------------------------------
                                 Name:   John McGhee
                                  Title: VP & Manager


                                BALANCED HIGH YIELD FUND I LTD. by BHF (USA)
                                Capital corporation acting as attorney-in-fact


                                By:
                                   ----------------------------------
                                 Name:
                                  Title:

                                By:
                                   ----------------------------------
                                 Name:
                                  Title:


                                BHF (USA) Capital Corporation


                                By:
                                   ----------------------------------
                                 Name:
                                  Title:

                                By:
                                   ----------------------------------
                                 Name:
                                  Title:




                                CIBC INC.


                                By:      /s/ ROGER COLDEN
                                   ----------------------------------
                                 Name:   Roger Colden
                                  Title: Authorized Signatory


<PAGE>   7

                                COMERICA BANK


                                By:      /s/ MARK B. GROVER
                                   ----------------------------------
                                 Name:   Mark B. Grover
                                  Title: Vice President



                                CREDIT LYONNAIS NEW YORK BRANCH


                                By:      /s/ PHILIPPE SOUSTRA
                                   ----------------------------------
                                 Name:   Philippe Soustra
                                  Title: Senior Vice President



                                FIRST HAWAIIAN BANK


                                By:       /s/ CHARLES L. JENKINS
                                   ----------------------------------
                                 Name:    Charles L. Jenkins
                                  Title:  Vice President, Manager


                                FIRST UNION NATIONAL BANK


                                By:       /s/ ROBERT R. WETTEROFF
                                   ----------------------------------
                                 Name:    Robert R. Wetteroff
                                  Title:  Senior Vice President


                                FROST NATIONAL BANK


                                By:       /s/ JENNIFER JENNINGS
                                   ----------------------------------
                                 Name:    Jennifer Jennings
                                  Title:  Credit Administrative Officer


                                THE FUJI BANK, LIMITED


                                By:       /s/ TEIJI TERAMOTO
                                   ----------------------------------
                                 Name:    Teiji Teramoto
                                  Title:  Vice President & Manager



<PAGE>   8

                                GUARANTY FEDERAL BANK


                                By:     /s/ JIM R. HAMILTON
                                   ----------------------------------
                                 Name:
                                  Title:


                                HIBERNIA NATIONAL BANK


                                By:      /s/ NANCY G. MORAGAS
                                   ----------------------------------
                                 Name:   Nancy G. Moragas
                                  Title: Assistant Vice President



                                THE INDUSTRIAL BANK OF JAPAN, LTD.


                                By:      /s/ MICHAEL N. OAKES
                                   ----------------------------------
                                 Name:   Michael N. Oakes
                                  Title: Senior Vice President,
                                         HOUSTON OFFICE


                                MEESPIERSON CAPITAL CORP.


                                By:      /s/ DEIRDRE SANBORN
                                   ----------------------------------
                                 Name:   Deirdre Sanborn
                                  Title: Vice President

                                By:      /s/ DARRELL W. HOLLEY
                                   ----------------------------------
                                 Name:   Darrell W. Holley
                                  Title: Managing Director


                                NATIONAL BANK OF ALASKA


                                By:      /s/ PATRICIA JELLEY BENZ
                                   ----------------------------------
                                 Name:   Patricia Jelley Benz
                                  Title: Vice President


                                NATIONAL BANK OF CANADA


                                By:      /s/ LARRY L. SEARS
                                   ----------------------------------
                                 Name:   Larry L. Sears
                                  Title: Vice President & Manager

                                By:      /s/ DOUG CLARK
                                   ----------------------------------
                                 Name:   Doug Clark
                                  Title: Vice President

<PAGE>   9

                                THE ROYAL BANK OF SCOTLAND


                                By:      /s/ SCOTT BARTON
                                   ----------------------------------
                                 Name:   Scott Barton
                                  Title: Vice President


                                SOCIETE GENERALE


                                By:      /s/ RICHARD A. GOULD
                                   ----------------------------------
                                 Name:   Richard A. Gould
                                  Title: Director



                                THE SUMITOMO BANK, LTD.


                                By:
                                   ----------------------------------
                                 Name:
                                  Title:


                                TORONOTO-DOMINION (TEXAS), INC.


                                By:      /s/ DEBBIE A. GREENE
                                   ----------------------------------
                                 Name:   Debbie A. Greene
                                  Title: Vice President


                                MOUNTAIN CLO TRUST


                                By:
                                   ----------------------------------
                                 Name:
                                  Title:



Schedule 4.15 listing Excluded Subsidiaries has been omitted. The Registrant
will furnish a copy of this omitted schedule to the Securities and Exchange
Commission upon request.