<PAGE>

                                                                    EXHIBIT 4.12

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN 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.

THIS GLOBAL SECURITY IS HELD BY THE DEPOSITORY (AS DEFINED IN THE INDENTURE
GOVERNING THIS SECURITY) OR ITS NOMINEE IN CUSTODY FOR THE BENEFIT OF THE
BENEFICIAL OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON UNDER ANY
CIRCUMSTANCES EXCEPT THAT (I) THE TRUSTEE MAY MAKE SUCH NOTATIONS HEREON AS MAY
BE REQUIRED PURSUANT TO SECTION 2.07 OF THE INDENTURE, (II) THIS GLOBAL SECURITY
MAY BE EXCHANGED IN WHOLE BUT NOT IN PART PURSUANT TO SECTION 2.07(a) OF THE
INDENTURE, (III) THIS GLOBAL SECURITY MAY BE DELIVERED TO THE TRUSTEE FOR
CANCELLATION PURSUANT TO SECTION 2.10 OF THE INDENTURE AND (IV) THIS GLOBAL
SECURITY MAY BE TRANSFERRED TO A SUCCESSOR DEPOSITORY WITH THE PRIOR WRITTEN
CONSENT OF THE COMPANY.

                           9 1/2% SENIOR NOTE DUE 2013

                         THE PREMCOR REFINING GROUP INC.

Cusip No. _______________                                   $

No. 1

         The Premcor Refining Group Inc., a corporation duly organized and
existing under the laws of Delaware (herein called the "Company," which term
includes any successor Person under the Indenture hereinafter referred to), for
value received, hereby promises to pay to CEDE & Co., or registered assigns, the
principal sum set forth above in United States Dollars on February 1, 2013 and
to pay interest thereon from February 11, 2003 or from the most recent Interest
Payment Date to which interest has been paid or as duly provided for,
semi-annually on February 1 and August 1 in each year, commencing August 1,
2003, at the rate of 9 1/2% per annum, until the principal hereof is paid or
made available for payment and such interest shall be payable on demand.


<PAGE>

         The interest so payable, and punctually paid or duly provided for, on
any Interest Payment Date will, as provided in such 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, which shall be the January 15 or July 15 (whether or not a Business
Day), as the case may be, next preceding such Interest Payment Date at the
office or agency of the Company at Deutsche Bank Trust Company Americas, 60 Wall
Street, New York, NY 10005 maintained for such purpose and at any other office
or agency maintained by the Company for such purpose (any such location being
called a "Place of Payment"); provided, however, that at the option of the
Company, payment of interest may be made by check to the address of the Person
entitled thereto as such address shall appear on the Security Register. Any such
interest not so punctually paid or duly provided, and interest on such defaulted
interest at the interest rate borne by the Securities, to the extent lawful,
shall forthwith cease to be payable to the Holder on such Regular Record Date
and shall be paid to the Person in whose name this Security (or one or more
Predecessor Securities) is registered at the close of business on a special
record date ("Special Record Date") for the payment of such defaulted interest
to be fixed by the Company with the consent of the Trustee, notice whereof shall
be given to Holders of Securities of this series not less than 10 days prior to
such Special Record Date, or may be paid at any time in any other lawful manner
not inconsistent with the requirements (if applicable) of any securities
exchange on which the Securities of this series may be listed, and upon such
notice as may be required by such securities exchange, all as more fully
provided in said Indenture.

         If this Security is a Global Security, all payments in respect of this
Security will be payable to the Global Security Holder in its capacity as the
registered Holder under the Indenture. If this Security is not a Global
Security, payment of the principal of, premium, if any, and interest on this
Security will be made at the office or agency of the Company maintained for that
purpose in the City and State of New York, 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, or at the option of the Company, payment of
interest may be made by check mailed to the address of the Person entitled
thereto as such address shall appear in the Security Register; provided,
however, that payment by wire transfer of immediately available funds will be
required with respect to principal of, premium, if any, and interest on, all
Global Securities and all other Securities the Holders of which shall have
provided wire transfer instructions to the Company or the Paying Agent.

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

         Unless the certificate of authentication hereon has been executed by
the Trustee by manual signature, this Security shall not be entitled to any
benefit under the Indenture or be valid or obligatory for any purpose.

                                       2


<PAGE>

         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

Dated:  ________  __, 2003

                                       THE PREMCOR REFINING GROUP INC.


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

Certificate of Authentication

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

                                       DEUTSCHE BANK TRUST COMPANY AMERICAS
                                                 as Trustee

                                       By
                                         ---------------------------------------
                                                 Authorized Signatory


<PAGE>

                              (Reverse of Security)

         This Security is one of a duly authorized issue of securities of the
Company (including the Additional Securities referred to below, herein called
the "Securities"), issued and to be issued in one or more series under an
Indenture, dated as of February 11, 2003 (herein called the "Indenture", which
term shall have the meaning assigned to it in such instrument), between the
Company and Deutsche Bank Trust Company Americas, as Trustee (herein called the
"Trustee", which term includes any successor trustee under the Indenture), and
reference is hereby made to the Indenture for a statement of the respective
rights, limitations of rights, duties and immunities thereunder of the Company,
the Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the series designated on the face hereof.

         The Company may issue additional securities (the "Additional
Securities") under the Indenture having the same terms in all respects as the
Securities (or in all respects except for the payment of interest on the
Securities (i) scheduled and paid prior to the date of issuance of such
Additional Securities or (ii) payable on the first Interest Payment Date
following such date of issuance). Such Additional Securities shall be treated as
part of the same series as the Securities for all purposes under the Indenture
and shall vote together with the Securities as part of the same class.

         The Securities of this series are subject to redemption upon not less
than 30 days' but no more than 60 days' notice by mail, at any time on or after
February 1, 2008, as a whole or in part, at the election of the Company, at the
following Redemption Prices (expressed as percentages of the principal amount),
if redeemed during the 12-month period beginning February 1 of the years
indicated,

                     Redemption
Year                   Price
----                 ----------


2008                   104.750%
2009                   103.167
2010                   101.583

and thereafter at a Redemption Price equal to 100.000% of the principal amount,
together in the case of any such redemption with accrued and unpaid interest to
the Redemption Date, but interest installments whose Stated Maturity is on or
prior to such Redemption Date shall be payable to the Holders of such
Securities, or one or more Predecessor Securities, of record at the close of
business on the

                                      R-1


<PAGE>

relevant Record Dates referred to on the face hereof, all as provided in the
Indenture.

         The Company may, at its option, use the net cash proceeds of one or
more Equity Offerings to the extent the net cash proceeds thereof are
contributed to the equity capital of the Company to redeem for cash up to 35% in
aggregate principal amount of the Securities originally issued under the
Indenture at any time prior to February 1, 2006, at a redemption price equal to
109.500% of the aggregate principal amount so redeemed, plus accrued interest,
including Special Interest, to the Redemption Date; provided that at least 65%
of the principal amount of Securities of such series originally issued remain
outstanding immediately after such redemption. Any such redemption shall be
required to occur on or prior to 120 days after the receipt by the Company of
the Net Available Proceeds of such Equity Offering and upon not less than 30 nor
more than 60 days' notice mailed to each holder of Securities to be redeemed at
such holder's address appearing in the Company's Security Register, in principal
amounts of $1,000 or an integral multiple of $1,000.

         If less than all of the Securities are to be redeemed at any time, the
Trustee shall select, in such manner as it shall deem fair and appropriate, the
particular Securities to be redeemed; provided that Securities redeemed in part
will only be redeemed in integral multiples of $1,000.

         The Indenture provides that, subject to certain conditions, if (i)
certain Net Available Proceeds are available to the Company as a result of Asset
Dispositions or (ii) a Change of Control Triggering Event occurs, the Company
shall be required to make an Offer to Purchase for some or all of the Securities
in accordance with the terms of the Indenture.

         The Indenture contains provisions for defeasance at any time of the
entire indebtedness of this Security or certain restrictive covenants and Events
of Default with respect to this Security, in each case upon compliance with
certain conditions set forth in the Indenture.

         In the event of redemption or purchase pursuant to a mandatory offer to
purchase this Security in part only, a new Security or Securities for the
unredeemed or unpurchased portion hereof will be issued in the name of the
Holder hereof upon the cancellation hereof.

         If an Event of Default with respect to Securities of this series shall
occur and be continuing, the principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture.

                                      R-2


<PAGE>

         The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of a majority in principal amount of the Securities at
the time Outstanding of each series to be affected. The Indenture also contains
provisions permitting the Holders of specified percentages in principal amount
of the Securities of each series at the time Outstanding, on behalf of the
Holders of all Securities of such series, to waive compliance by the Company
with certain provisions of the Indenture and certain past defaults under the
Indenture and their consequences. The Indenture also provides that, without
notice to or consent of any Holder, the Company and the Trustee may enter into
one or more supplemental indentures to, among other things, cure any ambiguity,
defect or inconsistency, provide for uncertificated securities in addition to or
in place of certificated Securities, or make any other change, in each case,
that does not adversely affect the rights of any Holder of a Security in any
material respect. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and of any Security issued upon the registration of transfer
hereof or in exchange therefor or in lieu hereof, whether or not notation of
such consent or waiver is made upon this Security.

         As provided in and subject to the provisions of the Indenture, the
Holder of this Security shall not have the right to institute any proceeding
with respect to the Indenture or for the appointment of a receiver or trustee or
for any other remedy thereunder, unless such Holder shall have previously given
the Trustee written notice of a continuing Event of Default with respect to the
Securities of this series, the Holders of not less than 25% in principal amount
of the Securities of this series at the time Outstanding shall have made written
request to the Trustee to institute proceedings in respect of such Event of
Default as Trustee and offered the Trustee reasonable indemnity, and the Trustee
shall not have received from the Holders of a majority in principal amount of
Securities of this series at the time Outstanding a direction inconsistent with
such request, and the Trustee shall have failed to institute any such
proceeding, for 60 days after receipt of such notice, request and offer of
indemnity. The foregoing shall not apply to any suit instituted by the Holder of
this Security for the enforcement of any payment of principal hereof or any
premium or interest hereon on or after the respective due dates expressed
herein.

         No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal of and any premium and

                                      R-3


<PAGE>

interest on this Security at the times, place and rate, and in the coin or
currency, herein prescribed.

         As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Company in any place where the principal of and any
premium and interest, including any Special Interest, on this Security are
payable, duly endorsed by, or accompanied by a written instrument of transfer in
form satisfactory to the Company and the Security Registrar duly executed by,
the Holder hereof or his attorney duly authorized in writing, and thereupon one
or more new Securities of this series and of like tenor, of authorized
denominations and for the same aggregate principal amount, shall be issued to
the designated transferee or transferees.

         The Securities of this series are issuable only in registered form
without coupons in denominations of $1,000 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
Securities of this series are exchangeable for a like aggregate principal amount
of Securities of this series and of like tenor of a different authorized
denomination, as requested by the Holder surrendering the same.

         No service charge shall be made to the Holder for any such registration
of transfer or exchange, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

         Prior to due presentment of this Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee may treat
the Person in whose name this Security is registered as the owner hereof for all
purposes, whether or not this Security be overdue, and none of the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

         No director, officer, employee, stockholder or incorporator, as such,
of the Company shall have any liability for any obligations of the Company under
the Securities or the Indenture for any claim based on, in respect of or by
reason of such obligations or their creation. Each Holder by accepting a
Security waives and releases all such liability. Such waiver and release are
part of the consideration for the issuance of the Securities.

         Interest on this Security shall be computed on the basis of a 360-day
year comprised of twelve 30-day months.

                                      R-4


<PAGE>

         All terms used in this Security that are defined in the Indenture shall
have the meanings assigned to them in the Indenture.

         The Indenture and this Security shall be governed by and construed in
accordance with the laws of the State of New York (without giving effect to
conflicts of law principles thereof).

                                      R-5


<PAGE>

                       OPTION OF HOLDER TO ELECT PURCHASE

         If you want to elect to have this Security purchased in its entirety by
the Company pursuant to Sections 10.08 and 9.13 of the Indenture, check the box:
[_]

         If you want to elect to have only a part of this Security purchased by
the Company pursuant to Sections 10.08 and 9.13 of the Indenture, state the
amount (which must be $1,000 or integral multiples thereof):
$____________________.

  Dated: ___________    Your Signature:
                                      ------------------------------------------
                                      (Sign exactly as name appears on the other
                                      side of this Security)

Signature Guarantee:
                      ----------------------------------------------------------
                      (Signature must be guaranteed by a member firm of a
                       national securities exchange or a commercial bank or
                       trust company)

                                      R-6


<PAGE>

                                 ASSIGNMENT FORM

To assign this Security, fill in the form below: (I) or (we) assign and transfer
this Security to



--------------------------------------------------------------------------------
                  (Insert assignee's soc. sec. or tax I.D. no.)


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

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

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

  Dated:             Your Signature:
                                     -------------------------------------------
                           (Sign exactly as name appears on the other side of
                            this Security)
Signature Guarantee:

                                      R-7


<PAGE>

                       SCHEDULE OF EXCHANGES OF SECURITIES

                  The following exchanges of a part of this Global Security for
another Global Security or for Definitive Securities have been made:


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

</TABLE>






                                      R-8