<PAGE>   1
                                                                     EXHIBIT 4.9


                           VALERO ENERGY CORPORATION

                             OFFICERS' CERTIFICATE

    This Officer's Certificate is being executed and delivered (a) pursuant to
Sections 102, 301 and 303 of the Indenture dated as of December 12, 1997 (the
"Indenture") by and between Valero Energy Corporation, a Delaware corporation
(the "Company"), and The Bank of New York, as trustee (the "Trustee"), and (b)
in connection with the order dated June 29, 2000 by the Company to the Trustee
(the "Order") for the authentication and delivery by the Trustee of
$200,000,000 aggregate principal amount of the Company's 8 3/8% Notes due 2005
and $200,000,000 aggregate principal amount of the Company's 8 3/4% Notes due
2030 (collectively, the "Notes"). The undersigned hereby certify that they are
the duly elected or appointed and acting Vice President and Chief Financial
Officer and the duly elected or appointed and acting Secretary of the Company,
respectively, and further certify that:

         (a). As of June 23, 2000, other terms of the Notes (including the form
    of the Notes) set forth in Annex A hereto were established by the Special
    Committee designated by the Board of Directors of the Company.

         (b). The undersigned have read Sections 102, 301 and 303 of the
    Indenture and the definitions in the Indenture relating thereto.

         (c). The statements made herein are based either upon the personal
    knowledge of the persons making this Certificate or on information, data
    and reports furnished to such persons by the officers, counsel, department
    heads or employees of the Company who have knowledge of the facts involved.

         (d). The undersigned have examined the Order, and they have examined
    the covenants, conditions and provisions of the Indenture relating thereto.

         (e). In the opinion of the undersigned, they have made such examination
    or investigation as is necessary to enable them to express an informed
    opinion as to whether or not all conditions provided for in the Indenture
    with respect to the authentication of the Notes have been complied with.

         (f). In the opinion of the undersigned, all conditions precedent
    provided in the Indenture to the authentication by the Trustee of the Notes
    have been complied with.

<PAGE>   2
        IN WITNESS WHEREOF, the undersigned have executed this certificate as of
this 29th day of June, 2000.



                                        /s/ JOHN D. GIBBONS
                                        ------------------------
                                        John D. Gibbons
                                        Vice President and Chief
                                        Financial Officer



                                        /s/ JAY D. BROWNING
                                        ------------------------
                                        Jay D. Browning
                                        Secretary


<PAGE>   3
                                    ANNEX A

                           VALERO ENERGY CORPORATION

                             8 3/8% Notes due 2005
                             8 3/4% Notes due 2030

         Two series of Securities are hereby established pursuant to Section
301 of the Indenture dated as of December 12, 1997 (the "Indenture"), between
Valero Energy Corporation, a Delaware corporation (the "Company"), and The Bank
of New York, as Trustee (in such capacity, the "Trustee"), as follows
(capitalized terms used and not defined herein shall have the meanings assigned
to them in the Indenture, and all references herein to a Section shall refer to
the corresponding Section in the Indenture):

1. The title of the 8 3/8% Notes due 2005 shall be "8 3/8% Notes due 2005" (the
"2005 Notes"), and the title of the 8 3/4% Notes due 2030 shall be "8 3/4% Notes
due 2030" (the "2030 Notes" and together with the 2005 Notes, the "Notes").

2. The limit upon the aggregate principal amount of the 2005 Notes that may be
authenticated and delivered under the Indenture (except for 2005 Notes
authenticated and delivered upon registration of transfer of, or in exchange
for, or in lieu of, other 2005 Notes pursuant to Sections 304, 305, 306, 906 or
1207) is $200,000,000.

3. The limit upon the aggregate principal amount of the 2030 Notes that may be
authenticated and delivered under the Indenture (except for 2030 Notes
authenticated and delivered upon registration of transfer of, or in exchange
for, or in lieu of, other 2030 Notes pursuant to Sections 304, 305, 306, 906 or
1207) is $200,000,000.

4. Each series of Notes shall be initially issued as Registered Securities in
the form of one or more global securities under the Indenture. The Depository
Trust Company is hereby designated as the Depository for these global
Securities under the Indenture.

         As long as any Note is in global form, then, notwithstanding clause
(11) of Section 301 and the provisions of Section 302, any such global Note
shall represent such of the outstanding Notes as shall be specified therein and
may provide that it shall represent the aggregate amount of outstanding Notes
from time to time endorsed thereon and that the aggregate amount of outstanding
Notes represented thereby may from time to time be reduced to reflect
exchanges. Any endorsement of a global Note to reflect the amount, or any
increase or decrease in the amount, of outstanding Notes represented thereby
shall be made by the Trustee in such manner and upon instructions given by such
Person or Persons as shall be specified in such Note or in a Company Order to
be delivered to the Trustee pursuant to Section 303. Subject to the provisions
of Section 303 and, if applicable Section 304, the Trustee shall deliver and
redeliver any Note in permanent global form in the manner and upon instructions
given by the Person or Persons specified in such Note or in the applicable
Company Order. With respect to the Notes of any series that are represented by
a global Note, the Company authorizes the execution and delivery by the Trustee
of a letter of representations or other similar agreement or instrument in the
form customarily provided for by the Depository appointed with respect to such
global Note. Any global Note may be deposited with the Depository or its
nominee, or may remain in the custody of the Trustee pursuant to a FAST Balance
Certificate Agreement or similar agreement between the Trustee and the
Depository. If a Company Order has been, or simultaneously is, delivered, any
instructions by the Company with respect to endorsement or delivery or
redelivery of a Note in global form shall be in writing but need not comply
with Section 102 and need not be accompanied by an Opinion of Counsel.

         Members of, or participants in, the Depository ("Agent Members") shall
have no rights under the Indenture with respect to any global Note held on
their behalf by the Depository, or the Trustee as its custodian, or under such
global Note and the Depository may be treated by the Company, the Trustee and
any agent of the Company or the Trustee as the absolute owner of such global
Note for all purposes whatsoever. Notwithstanding the foregoing, (i) the
registered holder of a global Note may grant proxies and otherwise authorize
any Person, including Agent Members and Persons that may hold interests through
an Agent Member, to take any action that a Holder is entitled to take under the
Indenture or the Notes and (ii) nothing herein shall prevent the Company, the
Trustee or any agent of the Company or the Trustee, from giving effect to any
written certification, proxy or other authorization furnished by the Depository
or shall impair, as between the Depository and its Agent Members, the operation
of customary practices governing the exercise of the rights of a beneficial
owner of any Note.



<PAGE>   4

         Notwithstanding Section 305, and except as otherwise provided pursuant
to Section 301, transfers of a global Note shall be limited to transfers of
such global Note in whole but not in part, to the Depository, its successors or
their respective nominees. Interests of beneficial owners in a global Note may
be transferred in accordance with the rules and procedures of the Depository.
In all other respects, Notes shall be transferred to all beneficial owners in
exchange for their beneficial interest in a Global Security solely as expressly
provided in Section 305.

         In connection with any transfer of a portion of the beneficial
interest in a global Note to beneficial owners pursuant hereto and Section 305,
the Security Registrar shall reflect on its books and records the date and a
decrease in the principal amount of the global Note of the applicable series in
an amount equal to the principal amount of the beneficial interest in the
global Note to be transferred, and the Company shall execute, and the Trustee
upon receipt of a Company Order for the authentication and delivery of Notes
shall authenticate and deliver, one or more Notes of like tenor and amount.

         In connection with the transfer of an entire global Note to beneficial
owners pursuant hereto and Section 305, the global Security shall be deemed to
be surrendered to the Trustee for cancellation, and the Company shall execute,
and the Trustee shall authenticate and deliver, to each beneficial owner
identified by the Depository in exchange for its beneficial interest in the
global Note, an equal aggregate principal amount of Notes of the applicable
series of authorized denominations.

         Neither the Company nor the Trustee will have any responsibility or
liability for any aspect of the records relating to, or payments made on
account of, Notes by the Depository, or for maintaining, supervising or
reviewing any records of the Depository relating to such Notes. Neither the
Company nor the Trustee shall be liable for any delay by the related global
Note Holder or the Depository in identifying the beneficial owners, and each
such Person may conclusively rely on, and shall be protected in relying on,
instructions from such global Note Holder or the Depository for all purposes
(including with respect to the registration and delivery, and the respective
principal amounts, of the Notes to be issued).

         Notwithstanding the provisions of Sections 201 and 307, unless
otherwise specified as contemplated by Section 301, payment of principal of,
premium (if any) or interest on any global Note shall be made to the Person or
Persons specified in such global Note.

5. The dates on which the principal of the 2005 Notes and the 2030 Notes are
payable shall be June 15, 2005 and June 15, 2030, respectively.

6. The rate at which the 2005 Notes shall bear interest shall be 8 3/8% per
annum and the rate at which the 2030 Notes shall bear interest shall be 8 3/4%
per annum. Interest will be computed on the basis of a 360-day year of twelve
30-day months. The date from which interest shall accrue for the Notes shall be
June 29, 2000. The Interest Payment Dates on which interest on the Notes shall
be payable are June 15 and December 15, commencing December 15, 2000. Interest
on the Notes shall be payable to the persons in whose name the Notes are
registered at the close of business on the Regular Record Date for such
interest payment, except in the case of default interest, which will be payable
as provided in the Indenture. The Regular Record Date for the interest payable
on the Notes on any Interest Payment Date shall be the June 1 and December 1,
as the case may be, immediately preceding such Interest Payment Date. No
Additional Amounts shall be payable with respect to the Notes.

7. The place or places where the principal of, premium (if any) and interest on
the Notes shall be payable is at the office or agency of the Trustee in New
York, New York or such other offices or agencies maintained for such purpose as
the Company may from time to time and in accordance with the Indenture
designate. If appropriate wire transfer instructions have been received by the
Trustee at its Corporate Trust Office or at its corporate trust facility in the
Borough of Manhattan, The City of New York, not later than 5 Business Days
prior to the record date for an applicable Interest Payment Date, then payments
in respect of the Notes evidenced by a global Security (including principal,
premium, if any, and interest) shall be made by wire transfer of immediately
available funds to the accounts specified by the Holder of such global Note. In
all other cases, payment of interest on the Notes may be made at the option of
the Company by check mailed to the address of the person entitled thereto as
such address shall appear in the Security Register.

8. Each series of Notes will be redeemable, in whole or in part, at the option
of the Company at any time, at a redemption price equal to the greater of (i)
100% of the principal amount of the applicable series of Notes, and (ii) as

<PAGE>   5

determined by the Quotation Agent (as defined below), the sum of the present
values of the remaining scheduled payments of principal and interest thereon
(not including any portion of such payments of interest accrued as of the date
of redemption) discounted to the date of redemption on a semi-annual basis
(assuming a 360-day year consisting of twelve 30-day months) at the Adjusted
Treasury Rate (as defined below) plus 25 basis points with respect to the 2005
Notes and 37.5 basis points with respect to the 2030 Notes plus, in each case,
accrued interest thereon to the date of redemption.

         "Adjusted Treasury Rate" means, with respect to any date of
         redemption, the rate per annum equal to the semi-annual equivalent
         yield to maturity of the Comparable Treasury Issue, assuming a price
         for the Comparable Treasury Issue (expressed as a percentage of its
         principal amount) equal to the Comparable Treasury Price for such date
         of redemption.

         "Comparable Treasury Issue" means the United States Treasury security
         selected by the Quotation Agent as having a maturity comparable to the
         remaining term of the series of Notes to be redeemed that would be
         utilized, at the time of selection and in accordance with customary
         financial practice, in pricing new issues of corporate debt securities
         of comparable maturity to the remaining term of such Notes.

         "Comparable Treasury Price" means, with respect to any date of
         redemption, (i) the average of the Reference Treasury Dealer
         Quotations for such date of redemption, after excluding the highest
         and lowest such Reference Treasury Dealer Quotations, or (ii) if the
         Trustee obtains fewer than three such Reference Treasury Dealer
         Quotations, the average of all such Reference Treasury Dealer
         Quotations.

         "Quotation Agent" means the Reference Treasury Dealer appointed by the
         Company.

         "Reference Treasury Dealers" means (i) each of J. P. Morgan Securities
         Inc., Credit Suisse First Boston Corporation, and Morgan Stanley & Co.
         Incorporated and their respective successors; provided, however, that
         if any of the foregoing shall cease to be a primary U.S. Government
         securities dealer in New York City (a "Primary Treasury Dealer"), the
         Company shall substitute therefor another Primary Treasury Dealer; and
         (ii) any other Primary Treasury Dealer selected by the Company.

         "Reference Treasury Dealer Quotations" means, with respect to each
         Reference Treasury Dealer and any date of redemption, the average, as
         determined by the Trustee, of the bid and asked prices for the
         Comparable Treasury Issue (expressed in each case as a percentage of
         its principal amount) quoted in writing to the Trustee by such
         Reference Treasury Dealer at 5:00 p.m., New York City time, on the
         third Business Day preceding such date of redemption.

         Notice of any redemption will be mailed at least 30 days but not more
         than 60 days before the date of redemption to each Holder of the
         applicable series of Notes to be redeemed. Unless the Company defaults
         in payment of the redemption price, on and after the date of
         redemption, interest will cease to accrue on the Notes or portions
         thereof called for redemption.

9. The Notes shall not be entitled to the benefit of any sinking fund, any
optional repurchase or redemption right in favor of any holder thereof or other
mandatory repurchase or redemption provisions.

10. The Notes shall be in substantially the form of Attachment A hereto (the
"Form of Note").

11. Each Note that is a global Security shall bear the legend set forth on the
face of the Form of Note.

<PAGE>   6

                                                  ATTACHMENT A TO TERMS OF NOTE

                               [FACE OF SECURITY]

         THIS SECURITY IS A GLOBAL SECURITY AS PROVIDED FOR IN THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY OR A
NOMINEE OF A DEPOSITORY. THIS SECURITY IS EXCHANGEABLE FOR SECURITIES
REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE
ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER
OF THIS SECURITY (OTHER THAN A TRANSFER OF THIS SECURITY AS A WHOLE BY THE
DEPOSITORY TO A NOMINEE OF THE DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO
THE DEPOSITORY OR ANOTHER NOMINEE OF THE DEPOSITORY) MAY BE REGISTERED EXCEPT
IN SUCH LIMITED CIRCUMSTANCES.

         UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO ISSUER OR
ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY
CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME
AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE
TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

                           VALERO ENERGY CORPORATION

                            ______% NOTES(1) DUE 20_

REGISTERED                                                             CUSIP No.

         VALERO ENERGY CORPORATION, a Delaware corporation (the "Company,"
which term includes any successor Person under the Indenture hereinafter
referred to), for value received promises to pay to Cede & Co. or registered
assigns, the principal sum of ____________ Dollars or such lesser amount as
indicated on the schedule of exchanges of definitive Securities, on _________,
20__.

              Interest Payment Dates: _________ 15 and ________ 15

               Regular Record Dates: __________ 1 and _________ 1

         Reference is hereby made to the further provisions of this Security
set forth in the reverse hereof, which further provisions shall for all
purposes have the same effect as if set forth at this place.

----------

    (1)   Two Notes will be issued if the Notes are issued as a single series
          in the principal amount of $___ million: a $___ million Note to be
          registered "R-001" and a $___ million Note to be registered "R-002".

<PAGE>   7

          IN WITNESS WHEREOF, the Company has caused this Security to be signed
manually or by facsimile by its duly authorized officers and its corporate seal
or a facsimile thereof to be affixed hereto or imprinted hereon.

Dated:          , 2000
      ----------
[SEAL]                                               VALERO ENERGY CORPORATION


                                                     By:(2)
                                                           ---------------------
                                                           Name:
                                                           Title:


ATTEST:


By:(3)
      ----------------------------
         Name:
         Title:



                    TRUSTEE'S CERTIFICATE OF AUTHENTICATION:

This is one of the Securities of the series designated therein referred to in
the within-mentioned Indenture.

                                                THE BANK OF NEW YORK, as Trustee

Dated:           , 2000                         By:
      -----------                                  -----------------------------
                                                        Authorized Signatory


----------

    (2)   Executed by Chairman of Board, President, Vice President serving as
          Chief Financial Officer or Treasurer.

    (3)   Attested by Secretary or one of the Assistant Secretaries.

<PAGE>   8

                             [REVERSE OF SECURITY]

                           VALERO ENERGY CORPORATION

                              _____% NOTES DUE 20_

         This Security is one of a duly authorized issue of debentures, notes
or other evidences of indebtedness of VALERO ENERGY CORPORATION, a Delaware
corporation (the "Company"), issued under the Indenture hereinafter referred to
and is one of a series of such debentures, notes or other evidences of
indebtedness designated pursuant thereto as __% Notes due 20__ (the
"Securities") of the Company.

         1. Interest. The Company promises to pay interest on the principal
amount of this Security at ____% per annum from ________, 2000 until Maturity
of the Securities. The Company will pay interest semiannually on _______ and
________ of each year (each an "Interest Payment Date") and on the Maturity of
the Securities, or if any such day is not a Business Day, on the next
succeeding Business Day. Interest on the Securities will accrue from the most
recent Interest Payment Date on which interest has been paid or, if no interest
has been paid, from ________, 2000; provided that if there is no existing
Default in the payment of, or provisions for, interest, and if this Security is
authenticated between a Regular Record Date referred to on the face hereof
(whether or not a Business Day) and the next succeeding Interest Payment Date,
interest shall accrue from such next succeeding Interest Payment Date;
provided, further, that the first Interest Payment Date shall be ________,
2000. The interest so payable, and punctually paid or provided for, on any
Interest Payment Date will, as provided in the Indenture, be paid to the Person
in whose name this Security (or one or more Predecessor Securities) is
registered at the close of business on the Regular Record Date for such
interest as set forth on the face hereof, provided, however, that interest
payable at Maturity of this Security will be payable to the Person to whom the
principal hereof shall be payable. Any such interest which is so payable, but
is not punctually paid or duly provided for on any Interest Payment Date, shall
forthwith cease to be payable to the registered Holder on such Regular Record
Date, and may be paid as more fully provided in the Indenture. Interest will be
computed on the basis of a 360-day year of twelve 30-day months.

         2. Method of payment. Payment of the principal of (and premium, if
any) and interest on this Security will be made at the office or agency of the
Company maintained for that purpose at the Corporate Trust Office of the
Trustee in the Borough of Manhattan, The City of New York, or at such other
offices or agencies maintained for such purpose as the Company may from time to
time and in accordance with the Indenture designate, in such coin or currency
of the United States of America as at the time of payment is legal tender for
payment of public and private debts; provided, however, that (i) payment of
interest may, at the option of the Company, be made (subject to collection) by
check mailed to the address of the Person entitled thereto as such address
shall appear on the Security Register or, with respect to Securities evidenced
by a global Security, if appropriate wire transfer instructions have been
received in writing by the Trustee at its Corporate Trust Office or at its
corporate trust facility in the Borough of Manhattan, The City of New York, not
later than 5 Business Days prior to the record date for an applicable Interest
Payment Date, be made by wire transfer of immediately available funds in
accordance with such wire transfer instructions; and (ii) payment of available
funds upon surrender of this Security will be made at the Corporate Trust
Office of the Trustee or at the corporate trust facility of the Trustee located
in the Borough of Manhattan, The City of New York, or at such additional
offices or agencies maintained for such purpose as the Company may from time to
time and in accordance with the Indenture designate.

         3. Certain Office. Initially, The Bank of New York, the Trustee under
the Indenture (in such capacity, the "Trustee"), will, at its Corporate Trust
Office in the Borough of Manhattan, The City of New York, act as the Company's
office or agency where the Securities may be presented or surrendered for
payment, where the Securities may be surrendered for registration of transfer
or exchange and where notices and demands to or upon the Company in respect of
the Securities and the Indenture may be served.

         4. Indenture. The Company issued the Securities under an Indenture
dated as of December 12, 1997 (the "Indenture") between the Company and the
Trustee. The terms of the Securities include those stated in the Indenture
(including terms defined therein, which terms when used herein, unless the
context requires otherwise, shall have the meanings assigned to such terms in
the Indenture) and those made part of the Indenture by reference to the Trust
Indenture Act of 1939, as amended (15 U.S. Code Sections 77aaa-77bbbb) (the
"TIA"), as in effect on the date of execution of the Indenture. The Securities
are subject to all such terms, and Holders are referred to the Indenture and the
TIA for a statement of such terms. The Securities are unsecured general
obligations of the Company limited to $________ in

<PAGE>   9

aggregate principal amount and will rank on a parity with all other unsecured
and unsubordinated indebtedness of the Company. The Indenture provides for the
issuance of other series of debentures, notes and other evidences of
Indebtedness (including the Securities, the "Debt Securities") thereunder.

         5. Denominations, Transfer, Exchange. The Securities are in registered
form without coupons and, if not in global form, in denominations of $1,000 and
integral multiples of $1,000. The transfer of Securities may be registered and
Securities may be exchanged as provided in the Indenture. The Security
Registrar and the Trustee may require a Holder, among other things, to furnish
appropriate endorsements and transfer documents and to pay any taxes and fees
required by law or permitted by the Indenture. The Security Registrar need not
exchange or register the transfer of any Securities during the period beginning
on the opening of business 15 days before the day of mailing of a notice of
redemption of the Securities and ending at the close of business on the day of
such mailing or of any Securities selected for redemption, except the
unredeemed portion of any Securities being redeemed in part.

         6. Persons Deemed Owners. The Holder of a Security shall be treated as
its owner for all purposes.

         7. Redemption. The Securities will be redeemable, in whole or in part,
at the option of the Company at any time, at a redemption price equal to the
greater of (i) 100% of the principal amount of such Securities, and (ii) as
determined by the Quotation Agent (as defined below), the sum of the present
values of the remaining scheduled payments of principal and interest thereon
(not including any portion of such payments of interest accrued as of the date
of redemption) discounted to the date of redemption on a semi-annual basis
(assuming a 360-day year consisting of twelve 30-day months) at the Adjusted
Treasury Rate (as defined below) plus ____ basis points plus, in each case,
accrued interest thereon to the date of redemption.

         "Adjusted Treasury Rate" means, with respect to any date of
         redemption, the rate per annum equal to the semi-annual equivalent
         yield to maturity of the Comparable Treasury Issue, assuming a price
         for the Comparable Treasury Issue (expressed as a percentage of its
         principal amount) equal to the Comparable Treasury Price for such date
         of redemption.

         "Comparable Treasury Issue" means the United States Treasury security
         selected by the Quotation Agent as having a maturity comparable to the
         remaining term of the Securities to be redeemed that would be
         utilized, at the time of selection and in accordance with customary
         financial practice, in pricing new issues of corporate debt securities
         of comparable maturity to the remaining term of such Securities.

         "Comparable Treasury Price" means, with respect to any date of
         redemption, (i) the average of the Reference Treasury Dealer
         Quotations for such date of redemption, after excluding the highest
         and lowest such Reference Treasury Dealer Quotations, or (ii) if the
         Trustee obtains fewer than three such Reference Treasury Dealer
         Quotations, the average of all such Reference Treasury Dealer
         Quotations.

         "Quotation Agent" means the Reference Treasury Dealer appointed by the
         Company.

         "Reference Treasury Dealers" means (i) each of J. P. Morgan Securities
         Inc., Credit Suisse First Boston Corporation and Morgan Stanley & Co.
         Incorporated and their respective successors; provided, however, that
         if any of the foregoing shall cease to be a primary U.S. Government
         securities dealer in New York City (a "Primary Treasury Dealer"), the
         Company shall substitute therefor another Primary Treasury Dealer; and
         (ii) any other Primary Treasury Dealer selected by the Company.

         "Reference Treasury Dealer Quotations" means, with respect to each
         Reference Treasury Dealer and any date of redemption, the average, as
         determined by Trustee, of the bid and asked prices for the Comparable
         Treasury Issue (expressed in each case as a percentage of its
         principal amount) quoted in writing to the Trustee by such Reference
         Treasury Dealer at 5:00 p.m., New York City time, on the third
         Business Day preceding such date of redemption.

Notice of any redemption will be mailed at least 30 days but not more than 60
days before the date of redemption to each Holder of the Securities to be
redeemed. Unless the Company defaults in payment of the redemption price, on
and after the date of redemption, interest will cease to accrue on the
Securities or portions thereof called for redemption.


<PAGE>   10

         8. Amendments and Waivers. Subject to certain exceptions and
limitations, the Indenture or the Securities may be supplemented with the
consent of the Holders of not less than a majority in aggregate principal
amount of the outstanding Securities, and any past default under the Indenture
with respect to the Securities, and its consequences, may be waived (other than
a default in the payment of the principal of (or premium, if any) or interest
on the Securities or in respect of a covenant or provision of the Indenture
which under Article 9 thereof cannot be modified or amended without the consent
of the Holder of each outstanding Security) by the Holders of not less than a
majority in principal amount of the outstanding Securities in accordance with
the terms of the Indenture. Without the consent of any Holder, the Company and
the Trustee may supplement the Indenture or the Securities (i) to cure any
ambiguity, omission, defect or inconsistency, in each case which shall not be
inconsistent with the provisions of the Indenture and which shall not adversely
affect the interest of the Holders of the Securities in any material respect;
(ii) to evidence the assumption by a successor Person of the obligations of the
Company under the Indenture and this Security; (iii) to change or eliminate any
restrictions on the payment of principal (or premium, if any) on Registered
Securities, to permit Registered Securities to be exchanged for Bearer
Securities or to permit the issuance of Securities in uncertificated form,
provided any such action shall not adversely affect the interest of the Holders
of the Securities in any material respect; (iv) to add to the covenants of the
Company for the benefit of the Holders of the Securities or Holders of other
series of Debt Securities, or to surrender any right or power conferred by the
Indenture upon the Company; (v) to add to, delete from or revise the
conditions, limitations and restrictions on the authorized amount, terms or
purpose of issue, authentication and delivery of the Securities as set forth in
the Indenture; or (vi) to evidence and provide for the acceptance of
appointment under the Indenture by a successor Trustee with respect to the
Securities and to add to or change any of the provisions of the Indenture as
shall be necessary to provide for or facilitate the administration of the
trusts thereunder by more than one Trustee, pursuant to the requirements of the
Indenture.

         The right of any Holder to participate in any consent required or
sought pursuant to any provision of the Indenture (and the obligation of the
Company to obtain any such consent otherwise required from such Holder) may be
subject to the requirement that such Holder shall have been the Holder of
record of any Securities with respect to which consent is required or sought as
of a date fixed in accordance with the terms of the Indenture.

         Subject to certain exceptions and limitations set forth in the
Indenture, without the consent of each Holder affected, the Company may not (i)
change the Stated Maturity of the principal of or any installment of interest
on any Security, (ii) reduce the principal amount of, or any premium or
interest on, any Security, (iii) change any Place of Payment where, or the
currency in which, any Security or any premium or interest thereon is payable,
(iv) impair the right to institute suit for the enforcement of any payment with
respect to any Security after the Stated Maturity thereof (or, in the case of
redemption, on or after the applicable Redemption Date), (v) reduce the
percentage in principal amount of the outstanding Securities whose Holders must
consent to a supplement or waiver, or reduce the requirements in Section 1504
of the Indenture for quorum or voting, or make any change in the percentage of
principal amount of Securities necessary to waive compliance with certain
provisions of the Indenture or (vi) waive a continuing Default or Event of
Default in the payment of principal of or premium (if any) or interest on the
Securities.

         A supplemental indenture that changes or eliminates any covenant or
other provision of the Indenture which has expressly been included solely for
the benefit of one or more particular series of Debt Securities under the
Indenture, or which modifies the rights of the Holders of Debt Securities of
such series with respect to such covenant or other provision, shall be deemed
not to affect the rights under the Indenture of the Holders of Debt Securities
of any other series.

         9. Defaults and Remedies. Events of Default are defined in the
Indenture and generally include: (i) failure to pay principal of or any premium
on any Security when due and payable; (ii) failure to pay any interest on any
Security when due and payable, and the continuation of the default for 30 days;
(iii) failure to perform any other covenant, or breach of any warranty, of the
Company in the Indenture, continued for 60 days after written notice is given
or received as provided in the Indenture; (iv) certain events of bankruptcy,
insolvency, or reorganization; and (v) failure to pay at final maturity (after
the expiration of any applicable grace periods) or upon the declaration of
acceleration of payment of indebtedness for borrowed money of the Company or
any Subsidiary in excess of $25 million, if such indebtedness is not
discharged, or such acceleration is not annulled, within 10 days after written
notice. If any Event of Default at any time outstanding occurs and is
continuing, either the Trustee or the Holders of at least 25% in aggregate
principal amount of the then outstanding Securities may declare the principal
amount of all Securities to be due and payable immediately. At any time after a
declaration or occurrence of acceleration with respect to the Securities has
been made, but before a judgment or decree based on acceleration has been
obtained, the Holders of a majority in

<PAGE>   11

aggregate principal amount of the then outstanding Securities may, under
certain circumstances, rescind and annul the acceleration.

         Holders may not enforce the Indenture or the Securities except as
provided in the Indenture. The Trustee may require indemnity reasonably
satisfactory to it before it enforces the Indenture or the Securities. Subject
to certain limitations, Holders of a majority in principal amount of the then
outstanding Securities may direct the Trustee in its exercise of any trust or
power with respect to the Securities. The Trustee may withhold from Holders
notice of any continuing default (except a default in payment of principal,
premium (if any) or interest) if in good faith it determines that withholding
notice is in their interests. The Company must furnish an annual compliance
certificate to the Trustee. 10. Discharge Prior to Maturity. The Indenture with
respect to the Securities shall be discharged and canceled upon the payment of
all Securities and, as provided in the Indenture, shall be discharged except
for certain obligations upon the irrevocable deposit with the Trustee of funds
sufficient for such payment.

         10. Discharge Prior to Maturity. The Indenture with respect to the
Securities shall be discharged and canceled upon the payment of all Securities
and, as provided in the Indenture, shall be discharged except for certain
obligations upon the irrevocable deposit with the Trustee of funds sufficient
for such payment.

         11. Trustee Dealings with Company. The Trustee, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company or its Affiliates, and may otherwise deal with the
Company or its Affiliates, as if it were not Trustee.

         12. Authentication. This Security shall not be valid until
authenticated by the manual signature of an authorized signer of the Trustee.

         13. CUSIP Numbers. Pursuant to a recommendation promulgated by the
Committee on Uniform Security Identification Procedures, the Company has caused
CUSIP numbers to be printed on the Securities as a convenience to the Holders
of the Securities. No representation is made as to the correctness of such
numbers as printed on the Securities and reliance may be placed only on the
other identification numbers printed thereon.

         14. Abbreviations. Customary abbreviations may be used in the name of
a Holder or an assignee, such as: TEN COM (= tenants in common), TEN ENT (=
tenants by the entireties), JT TEN (= joint tenants with right of survivorship
and not as tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform gifts
to Minors Act).

         15. Restrictions on Transfer. By its acceptance of any Security
bearing a legend restricting transfer, each Holder of a Security acknowledges
the restrictions on transfer of such Security set forth in the officers'
certificate executed pursuant to Section 303 of the Indenture in respect of the
Securities and such legend and agrees that it will transfer such Security only
as provided in such officers' certificate and in the Indenture.

         THE COMPANY WILL FURNISH TO ANY HOLDER UPON WRITTEN REQUEST AND
WITHOUT CHARGE A COPY OF THE INDENTURE. REQUEST MAY BE MADE TO:

                  VALERO ENERGY CORPORATION
                  ONE VALERO PLACE
                  SAN ANTONIO, TEXAS 78212
                  TELEPHONE: (210) 370-2000
                  ATTENTION:  GENERAL COUNSEL



<PAGE>   12

                  SCHEDULE OF EXCHANGES OF DEFINITIVE SECURITY

         The following exchanges of a part of this global Security for
definitive Securities have been made:

<TABLE>
<CAPTION>

                                                                           Principal Amount of         Signature of
                          Amount of decrease in   Amount of increase in   this global Security    authorized officer of
                           Principal Amount of     Principal Amount of       following such        Trustee or Security
   Date of Exchange       this global Security    this global Security   decrease (or increase)         Registrar
   ----------------       --------------------    --------------------   ----------------------         ---------
<S>                      <C>                      <C>                    <C>                      <C>


</TABLE>

<PAGE>   13

                                ASSIGNMENT FORM

         To assign this Security, fill in the form below: (I) or (we) assign
and transfer this Security to __________________________ (Insert assignee's
social security or tax I.D. number)

-------------------------------------------------------------------------------

-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
             (Print or type assignee's name, address and zip code)

and irrevocably appoint ________________________ as agent to transfer this
Security on the books of the Company. The agent may substitute another to act
for him.


-------------------------------------------------------------------------------

Date:                                   Your Signature:
     -----------------                                  ---------------------
                                                        (Sign exactly as your
                                                        name appears on the face
                                                        of this Security)

Signature Guarantee:
                    ------------------------------------------------------------
                           (Participant in a Recognized Signature Guaranty
                                          Medallion Program)