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                                                                  EXECUTION COPY

                            PORT ARTHUR FINANCE CORP.

                                  $255,000,000

                  12.50% Senior Secured Exchange Notes due 2009

               Unconditionally Guaranteed Jointly and Severally by

                         PORT ARTHUR COKER COMPANY L.P.
                           SABINE RIVER HOLDING CORP.
                           NECHES RIVER HOLDING CORP.
                         THE PREMCOR REFINING GROUP INC.

                          REGISTRATION RIGHTS AGREEMENT

                                                                    June 6, 2002



HSBC Bank USA,
As Capital Markets Trustee
For the Capital Markets Senior Lenders Referred to Herein
452 Fifth Avenue,
New York, NY 10018-2706

Ladies and Gentlemen:

         Port Arthur Finance Corp., a Delaware corporation (the "Issuer"),
previously issued and sold an aggregate of $255,000,000 principal amount of its
12.50% Senior Secured Notes due 2009 (the "Initial Securities"), unconditionally
guaranteed jointly and severally by Port Arthur Coker Company L.P., a Delaware
limited partnership (the "Partnership"), Sabine River Holding Corp., a Delaware
corporation and the general partner of the Partnership (the "General Partner"),
Neches River Holding Corp., a Delaware corporation and the limited partner of
the Partnership (the "Limited Partner" and, together with the General Partner,
the "Partners"). The Initial Securities were issued pursuant to an indenture,
dated as of August 19, 1999 (as amended or supplemented, the "Indenture"), among
the Issuer, the Partnership, the Partners, HSBC Bank USA, as Capital Markets
Trustee for the Capital Markets Senior Lenders (the "Capital Markets Trustee"),
and Deutsche Bank Trust Company Americas (formerly known as "Bankers Trust
Company"), as Collateral Trustee for the Secured Parties (the "Collateral
Trustee"). In connection with certain amendments to the Indenture and certain
related documents, The Premcor Refining Group Inc. ("PRG") has agreed to
guarantee fully and unconditionally, on a senior unsecured basis, the Issuer's
payment obligations under the Initial Securities (the "PRG Guarantee"). Because
the PRG

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Guarantee has been offered in reliance on exemptions from registration under the
Securities Act of 1933, as amended (the "Securities Act"), and because, upon
the issuance of the PRG Guarantee, sales or other transfers of the Initial
Securities will become subject to certain restrictions, the Issuer, the
Partnership, the Partners and PRG agree with the Capital Markets Trustee, for
the benefit of the holders of the Initial Securities and the Exchange Securities
(as defined below) (collectively, the "Holders"), as follows:

         1. Registered Exchange Offer. Each of the Issuer, the Partnership, the
Partners and PRG (hereinafter referred to collectively as the "Issuer Group"),
jointly and severally, shall, at its own cost, prepare and, not later than 120
days after the effectiveness date of the PRG Guarantee (the "Effective Date"),
file with the Securities and Exchange Commission (the "Commission") a
registration statement (the "Exchange Offer Registration Statement") on an
appropriate form under the Securities Act, with respect to a proposed offer (the
"Registered Exchange Offer") to the Holders of Transfer Restricted Securities
(as defined in Section 6 hereof) who are not prohibited by any law or policy of
the Commission from participating in the Registered Exchange Offer to issue and
deliver to such Holders, in exchange for the Initial Securities (including the
related PRG Guarantee), a like aggregate principal amount of Exchange Securities
(including the PRG Guarantee, the "Exchange Securities") of the Issuer issued
under the Indenture, entitling the Holders thereof to the benefits of the PRG
Guarantee and identical in all material respects to the Initial Securities
(except for the transfer restrictions relating to the Initial Securities and the
provisions relating to the matters described in Section 6 hereof) but that are
registered under the Securities Act. The Issuer Group shall use its reasonable
best efforts to cause such Exchange Offer Registration Statement to become
effective under the Securities Act within 240 days after the Effective Date and
shall keep the Exchange Offer Registration Statement effective for not less than
20 business days (or longer, if required by applicable law) after the date
notice of the Registered Exchange Offer is mailed to the Holders (such period
being called the "Exchange Offer Registration Period").

         If the Issuer Group effects the Registered Exchange Offer, the Issuer
Group will be entitled to close the Registered Exchange Offer 20 business days
after the commencement thereof, provided that the Issuer Group has accepted all
the Initial Securities theretofore validly tendered in accordance with the terms
of the Registered Exchange Offer.

         Following the declaration of the effectiveness of the Exchange Offer
Registration Statement, the Issuer Group shall promptly commence the Registered
Exchange Offer, it being the objective of such Registered Exchange Offer to
enable each Holder of Transfer Restricted Securities (as defined in Section 6
hereof) electing to exchange the Initial Securities for Exchange Securities
(assuming that such Holder is not an affiliate of any member of the Issuer Group
within the meaning of the Securities Act, acquires the Exchange Securities in
the ordinary course of such Holder's business, has no arrangements with any
person to participate in the distribution of the Exchange Securities and is not
prohibited by any law or policy of the Commission from participating in the

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Registered Exchange Offer) to trade such Exchange Securities from and after
their receipt without any limitations or restrictions under the Securities Act
and without material restrictions under the securities laws of the several
states of the United States.

         The Issuer Group acknowledges that, pursuant to current interpretations
by the Commission's staff of Section 5 of the Securities Act, in the absence of
an applicable exemption therefrom, each Holder which is a broker-dealer electing
to exchange Initial Securities, acquired for its own account as a result of
market making activities or other trading activities, for Exchange Securities
(an "Exchanging Dealer"), is required to deliver a prospectus containing the
information set forth in (a) Annex A hereto on the cover, (b) Annex B hereto in
the "Exchange Offer Procedures" section and the "Purpose of the Exchange Offer"
section, and (c) Annex C hereto in the "Plan of Distribution" section of such
prospectus in connection with a sale of any such Exchange Securities received by
such Exchanging Dealer pursuant to the Registered Exchange Offer.

         The Issuer Group shall use its reasonable best efforts to keep the
Exchange Offer Registration Statement effective and to amend and supplement the
prospectus contained therein, in order to permit such prospectus to be lawfully
delivered by all persons subject to the prospectus delivery requirements of the
Securities Act for such period of time as such persons must comply with such
requirements in order to resell the Exchange Securities; provided, however, that
(i) in the case where such prospectus and any amendment or supplement thereto
must be delivered by an Exchanging Dealer, such period shall be the lesser of
120 days and the date on which all Exchanging Dealers have sold all Exchange
Securities held by them (unless such period is extended pursuant to Section 3(j)
below) and (ii) the Issuer Group shall make such prospectus and any amendment or
supplement thereto available to any broker-dealer for use in connection with any
resale of any Exchange Securities for a period of not less than 120 days after
the consummation of the Registered Exchange Offer.

         The Initial Securities and the Exchange Securities are herein
collectively called the "Securities".

         In connection with the Registered Exchange Offer, the Issuer Group
shall:

         (a) mail to each Holder a copy of the prospectus forming part of the
Exchange Offer Registration Statement, together with an appropriate letter of
transmittal and related documents;

         (b) keep the Registered Exchange Offer open for not less than 20
business days (or longer, if required by applicable law) after the date notice
thereof is mailed to the Holders;

         (c) utilize the services of a depositary for the Registered Exchange
Offer with an address in The City of New York, which may be the Capital Markets
Trustee or an affiliate of the Capital Markets Trustee;

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       (d) permit Holders to withdraw tendered Initial Securities at any time
prior to the close of business, New York time, on the last business day on which
the Registered Exchange Offer shall remain open; and

       (e) otherwise comply with all applicable laws.

       As soon as practicable after the close of the Registered Exchange Offer,
the Issuer Group shall:

       (x) accept for exchange all the Initial Securities validly tendered and
not withdrawn pursuant to the Registered Exchange Offer;

       (y) deliver to the Capital Markets Trustee for cancellation all the
Initial Securities so accepted for exchange; and

       (z) cause the Capital Markets Trustee to authenticate and deliver
promptly to each Holder of the Initial Securities, Exchange Securities equal in
principal amount to the Initial Securities of such Holder so accepted for
exchange.

       The Indenture provides that the Exchange Securities will not be subject
to the transfer restrictions set forth in the Indenture and that all the
Securities will vote and consent together on all matters as one class and that
none of the Securities will have the right to vote or consent as a class
separate from one another on any matter.

       Interest on each Exchange Security issued pursuant to the Registered
Exchange Offer will accrue from the last interest payment date on which interest
was paid on the Initial Securities surrendered in exchange therefor or, if no
interest has been paid on the Initial Securities, from the date of original
issue of the Initial Securities.

       Each Holder participating in the Registered Exchange Offer shall be
required to represent to the Issuer that at the time of the consummation of the
Registered Exchange Offer (i) any Exchange Securities received by such Holder
will be acquired in the ordinary course of business, (ii) such Holder will have
no arrangements or understanding with any person to participate in the
distribution of the Securities within the meaning of the Securities Act, (iii)
such Holder is not an "affiliate," as defined in Rule 405 of the Securities Act,
of any member of the Issuer Group or if it is an affiliate, such Holder will
comply with the registration and prospectus delivery requirements of the
Securities Act to the extent applicable, (iv) if such Holder is not a
broker-dealer, that it is not engaged in, and does not intend to engage in, the
distribution of the Exchange Securities and (v) if such Holder is a
broker-dealer, that it will receive Exchange Securities for its own account in
exchange for Initial Securities that were acquired as a result of market-making
activities or other trading activities and that it will be required to
acknowledge that it will deliver a prospectus in connection with any resale of
such Exchange Securities.

       Notwithstanding any other provisions hereof, the Issuer Group will ensure
that (i) any Exchange Offer Registration Statement and any amendment thereto and
any

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prospectus forming part thereof and any supplement thereto complies in all
material respects with the Securities Act and the rules and regulations
thereunder, (ii) any Exchange Offer Registration Statement and any amendment
thereto does not, when it becomes effective, contain an untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein not misleading and (iii) any prospectus
forming part of any Exchange Offer Registration Statement, and any supplement to
such prospectus, does not include an untrue statement of a material fact or omit
to state a material fact required to be stated therein or necessary in order to
make the statements therein, in the light of the circumstances under which they
were made, not misleading.

       2.  Shelf Registration. If, (i) because of any change in law or in
applicable interpretations thereof by the staff of the Commission, the Issuer
Group is not permitted to effect a Registered Exchange Offer, as contemplated by
Section 1 hereof, (ii) the Registered Exchange Offer is not consummated within
270 days of the Effective Date, (iii) any applicable law or interpretations do
not permit any Holder to participate in the Registered Exchange Offer, (iv) any
Holder that participates in the Registered Exchange Offer does not receive
freely tradeable Exchange Securities on the date of the exchange or (v) we so
elect, the Issuer Group shall take the following actions:

       (a) The Issuer Group shall, at its cost, as promptly as practicable (but
in no event less than 120 days after the Effective Date or more than 60 days
after so required or requested pursuant to this Section 2) file with the
Commission and thereafter shall use its reasonable best efforts to cause to be
declared effective a registration statement (the "Shelf Registration Statement"
and, together with the Exchange Offer Registration Statement, a "Registration
Statement") on an appropriate form under the Securities Act relating to the
offer and sale of the Transfer Restricted Securities (as defined in Section 6
hereof) by the Holders thereof from time to time in accordance with the methods
of distribution set forth in the Shelf Registration Statement and Rule 415 under
the Securities Act (hereinafter, the "Shelf Registration"); provided, however,
that no Holder shall be entitled to have the Securities held by it covered by
such Shelf Registration Statement unless such Holder agrees in writing to be
bound by all the provisions of this Agreement applicable to such Holder.

       (b) The Issuer Group shall use its reasonable best efforts to keep the
Shelf Registration Statement continuously effective in order to permit the
prospectus included therein to be lawfully delivered by the Holders of the
relevant Securities, for a period of two years (or for such longer period if
extended pursuant to Section 3(j) below) from the date of its effectiveness or
such shorter period that will terminate when all the Securities covered by the
Shelf Registration Statement (i) have been sold pursuant thereto or (ii) are no
longer restricted securities (as defined in Rule 144 under the Securities Act,
or any successor rule thereof). The Issuer Group shall be deemed not to have
used its reasonable best efforts to keep the Shelf Registration Statement
effective during the requisite period if it voluntarily takes any action that
would result in Holders of Securities covered

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thereby not being able to offer and sell such Securities during that period,
unless such action is required by applicable law.

      (c) Notwithstanding any other provisions of this Agreement to the
contrary, the Issuer Group shall cause the Shelf Registration Statement and the
related prospectus and any amendment or supplement thereto, as of the effective
date of the Shelf Registration Statement, amendment or supplement, (i) to comply
in all material respects with the applicable requirements of the Securities Act
and the rules and regulations of the Commission and (ii) not to contain any
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary in order to make the statements therein, in light
of the circumstances under which they were made, not misleading.

      3.  Registration Procedures. In connection with any Shelf Registration
contemplated by Section 2 hereof and, to the extent applicable, any Registered
Exchange Offer contemplated by Section 1 hereof, the following provisions shall
apply:

      (a) The Issuer Group shall (i) include the information set forth in Annex
A hereto on the cover, in Annex B hereto in the "Exchange Offer Procedures"
section and the "Purpose of the Exchange Offer" section and in Annex C hereto in
the "Plan of Distribution" section of the prospectus forming a part of the
Exchange Offer Registration Statement and include the information set forth in
Annex D hereto in the Letter of Transmittal delivered pursuant to the Registered
Exchange Offer; (ii) in the case of an Exchange Offer Registration Statement,
include within the prospectus contained therein a section entitled "Plan of
Distribution", which shall contain a summary statement of the positions taken or
policies made by the staff of the Commission with respect to the potential
"underwriter" status of any broker-dealer that is the beneficial owner (as
defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended (the
"Exchange Act")) of Exchange Securities received by such broker-dealer in the
Registered Exchange Offer (a "Participating Broker-Dealer"), whether such
positions or policies have been publicly disseminated by the staff of the
Commission or such positions or policies represent the prevailing views of the
staff of the Commission, and (iii) in the case of a Shelf Registration
Statement, include the names of the Holders who propose to sell Securities
pursuant to the Shelf Registration Statement as selling security holders.

      (b) The Issuer Group shall give notice to the Capital Markets Trustee, the
Holders of the Securities and any Participating Broker-Dealer from whom the
Issuer Group has received prior notice that it will be a Participating
Broker-Dealer in the Registered Exchange Offer (which notice pursuant to clauses
(ii)-(v) hereof shall be accompanied by an instruction to suspend the use of the
prospectus until the requisite changes have been made):

      (i) when the Registration Statement or any amendment thereto has been
filed with the Commission and when the Registration Statement or any
post-effective amendment thereto has become effective (which notice may be in
the form of a copy of such Registration Statement as filed or as it became
effective);

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       (ii)  after the effectiveness thereof, of any request by the Commission
for amendments or supplements to the Registration Statement or the prospectus
included therein or for additional information;

       (iii) of the issuance by the Commission of any stop order suspending the
effectiveness of the Registration Statement or the initiation of any proceedings
for that purpose;

       (iv)  of the receipt by the Issuer Group or its legal counsel of any
notification with respect to the suspension of the qualification of the
Securities for sale in any jurisdiction or the initiation or threatening of any
proceeding for such purpose; and

       (v)   after the effectiveness thereof, of the happening of any event that
requires the Issuer Group to make changes in the Registration Statement or the
prospectus in order that the Registration Statement or the prospectus do not
contain an untrue statement of a material fact nor omit to state a material fact
required to be stated therein or necessary to make the statements therein (in
the case of the prospectus, in light of the circumstances under which they were
made) not misleading.

       (c)   The Issuer Group shall make every reasonable effort to obtain the
withdrawal at the earliest possible time, of any order suspending the
effectiveness of the Registration Statement.

       (d)   The Issuer Group shall furnish to each Holder of Securities
included within the coverage of the Shelf Registration, without charge, at least
one copy of the Shelf Registration Statement and any post-effective amendment
thereto, including financial statements and schedules, and, if the Holder so
requests in writing and unless such exhibits are available under the EDGAR
system, all exhibits thereto (including those, if any, incorporated by
reference).

       (e)   The Issuer Group shall deliver to each Exchanging Dealer and the
Capital Markets Trustee, and to any other Holder who so requests in writing,
without charge, at least one copy of the Exchange Offer Registration Statement
as it became effective and any post-effective amendment thereto, including
financial statements and schedules, and, if the Capital Markets Trustee or any
such Holder requests in writing and unless such exhibits are available under the
EDGAR system, all exhibits thereto (including those incorporated by reference).

       (f)   The Issuer Group shall, during the Shelf Registration Period,
deliver to each Holder of Securities included within the coverage of the Shelf
Registration, without charge, as many copies of the prospectus (including each
preliminary prospectus) included in the Shelf Registration Statement and any
amendment or supplement thereto as such person may reasonably request. Each
member of the Issuer Group consents, subject to the provisions of this
Agreement, to the use of the prospectus or any amendment or supplement thereto
by each of the selling Holders of the Securities in

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connection with the offering and sale of the Securities covered by the
prospectus, or any amendment or supplement thereto, included in the Shelf
Registration Statement.

         (g) During the period described herein the Issuer Group shall deliver
to the Capital Markets Trustee, any Exchanging Dealer, any Participating
Broker-Dealer and such other persons required to deliver a prospectus following
the Registered Exchange Offer, without charge, as many copies of the final
prospectus included in the Exchange Offer Registration Statement and any
amendment or supplement thereto as such persons may reasonably request. The
Issuer Group consents, subject to the provisions of this Agreement, to the use
of the prospectus or any amendment or supplement thereto by any Participating
Broker-Dealer and such other persons required to deliver a prospectus following
the Registered Exchange Offer in connection with the offering and sale of the
Exchange Securities covered by the prospectus, or any amendment or supplement
thereto, included in such Exchange Offer Registration Statement.

         (h) Prior to any public offering of the Securities pursuant to any
Registration Statement the Issuer Group shall register or qualify or cooperate
with the Holders of the Securities included therein and their respective counsel
in connection with the registration or qualification of the Securities for offer
and sale under the securities or "blue sky" laws of such states of the United
States as any Holder of the Securities reasonably requests in writing and do any
and all other acts or things necessary or advisable to enable the offer and sale
in such jurisdictions of the Securities covered by such Registration Statement;
provided, however, that no member of the Issuer Group shall be required to (i)
qualify generally to do business in any jurisdiction where it is not then so
qualified or (ii) take any action which would subject it to general service of
process or to taxation in any jurisdiction where it is not then so subject.

         (i) The Issuer Group shall cooperate with the Holders of the Securities
to facilitate the timely preparation and delivery of certificates representing
the Securities to be sold pursuant to any Registration Statement free of any
restrictive legends and in such denominations and registered in such names as
the Holders may request a reasonable period of time prior to sales of the
Securities pursuant to such Registration Statement.

         (j) Upon the occurrence of any event contemplated by paragraphs (ii)
through (v) of Section 3(b) above during the period for which the Issuer Group
is required to maintain an effective Registration Statement, the Issuer Group
shall promptly prepare and file a post-effective amendment to the Registration
Statement or a supplement to the related prospectus and any other required
document so that, as thereafter delivered to Holders of the Securities or
purchasers of Securities, the prospectus will not contain an untrue statement of
a material fact or omit to state any material fact required to be stated therein
or necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading. If the Issuer Group notifies the Capital
Markets Trustee, the Holders of the Securities and any known Participating
Broker-Dealer in accordance with paragraphs (ii) through (v) of Section 3(b)
above to suspend the use of the prospectus until the requisite changes to the
prospectus have been made, then the

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Holders of the Securities and any such Participating Broker-Dealers shall
suspend use of such prospectus, and the period of effectiveness of the Shelf
Registration Statement provided for in Section 2(b) above and the Exchange Offer
Registration Statement provided for in Section 1 above shall each be extended by
the number of days from and including the date of the giving of such notice to
and including the date when the Capital Markets Trustee, the Holders of the
Securities and any known Participating Broker-Dealer shall have received such
amended or supplemented prospectus pursuant to this Section 3(j).

         (k) Not later than the effective date of the applicable Registration
Statement, the Issuer Group will provide a CUSIP number for the Initial
Securities or the Exchange Securities, as the case may be, and provide the
applicable trustee with certificates for the Initial Securities or the Exchange
Securities, as the case may be, in a form eligible for deposit with the Capital
Markets Trustee as custodian for The Depository Trust Company.

         (l) The Issuer Group will comply with all rules and regulations of the
Commission to the extent and so long as they are applicable to the Registered
Exchange Offer or the Shelf Registration and will make generally available to
its security holders (or otherwise provide in accordance with Section 11(a) of
the Securities Act) an earnings statement satisfying the provisions of Section
1l(a) of the Securities Act, no later than 45 days after the end of a 12-month
period (or 90 days, if such period is a fiscal year) beginning with the first
month of the Issuer's first fiscal quarter commencing after the effective date
of the Registration Statement, which statement shall cover such 12-month period.

         (m) The Issuer Group shall ensure that the Indenture continues to be
qualified under the Trust Indenture Act of 1939, as amended. In the event that
such continued qualification would require the appointment of a new trustee
under the Indenture, the Issuer Group shall appoint a new trustee thereunder
pursuant to the applicable provisions of the Indenture.

         (n) The Issuer Group may require each Holder of Securities to be sold
pursuant to the Shelf Registration Statement to furnish to the Issuer such
information regarding the Holder and the distribution of the Securities as the
Issuer Group may from time to time reasonably require for inclusion in the Shelf
Registration Statement, and the Issuer Group (i) may exclude from such
registration the Securities of any Holder that unreasonably fails to furnish
such information within a reasonable time after receiving such request and (ii)
shall not be obligated to pay Additional Interest on such Securities to such
Holder from the date of such failure.

         (o) The Issuer Group shall enter into such customary agreements
(including, if requested by the Holders of a majority in aggregate principal
amount of the Exchange Securities, an underwriting agreement in customary form)
and take all such other action, if any, as any Holder of the Securities shall
reasonably request in order to facilitate the

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disposition of the Securities pursuant to any Shelf Registration, provided that
the Issuer Group shall not be required to do more than one underwritten offering
in any 12-month period.

         (p) In the case of any Shelf Registration, the Issuer Group shall (i)
make reasonably available for inspection by the Holders of the Securities, any
underwriter participating in any disposition pursuant to the Shelf Registration
Statement and any attorney, accountant or other agent retained by the Holders of
the Securities or any such underwriter all relevant financial and other records,
pertinent corporate documents and properties of any member of the Issuer Group
and (ii) cause the officers, directors, employees, accountants and auditors of
any member of the Issuer Group to supply all relevant information reasonably
requested by the Holders of the Securities or any such underwriter, attorney,
accountant or agent in connection with the Shelf Registration Statement, in each
case, as shall be reasonably necessary to enable such persons, to conduct a
reasonable investigation within the meaning of Section 11 of the Securities Act.

         (q) In the case of any Shelf Registration, each member of the Issuer
Group, if requested by a managing underwriter or the Holders of a majority in
principal amount of the Securities covered thereby, shall cause (i) its counsel
to deliver an opinion and updates thereof relating to the Securities in
customary form addressed to such Holders and the managing underwriters, if any,
thereof and dated, in the case of the initial opinion, the effective date of
such Shelf Registration Statement (it being agreed that the matters to be
covered by such opinion shall include, without limitation, the due incorporation
and good standing of the Issuer Group and its subsidiaries; the qualification of
the members of the Issuer Group and their respective subsidiaries to transact
business as foreign corporations; the due authorization, execution and delivery
of the relevant agreement of the type referred to in Section 3(o) hereof; the
due authorization, execution, authentication and issuance, and the validity and
enforceability, of the applicable Securities; the absence of material legal or
governmental proceedings involving the members of the Issuer Group and their
respective subsidiaries; the absence of governmental approvals required to be
obtained in connection with the Shelf Registration Statement, the offering and
sale of the applicable Securities, or any agreement of the type referred to in
Section 3(o) hereof; the compliance as to form of such Shelf Registration
Statement and any documents incorporated by reference therein and of the
Indenture with the requirements of the Securities Act and the Trust Indenture
Act, respectively; and, as of the date of the opinion and as of the effective
date of the Shelf Registration Statement or most recent post-effective amendment
thereto, as the case may be, the absence from such Shelf Registration Statement
and the prospectus included therein, as then amended or supplemented, and from
any documents incorporated by reference therein of an untrue statement of a
material fact or the omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading (in
the case of any such documents, in the light of the circumstances existing at
the time that such documents were filed with the Commission under the Exchange
Act)); (ii) its officers to execute and deliver all customary documents and
certificates and updates thereof

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requested by any underwriters of the applicable Securities and (iii) its
independent public accountants and the independent public accountants with
respect to any other entity for which financial information is provided in the
Shelf Registration Statement to provide to the selling Holders of the applicable
Securities and any underwriter therefor a comfort letter in customary form and
covering matters of the type customarily covered in comfort letters in
connection with primary underwritten offerings, subject to receipt of
appropriate documentation as contemplated, and only if permitted, by Statement
of Auditing Standards No. 72.

         (r) If a Registered Exchange Offer is to be consummated, upon delivery
of the Initial Securities by Holders to the Issuer (or to such other Person as
directed by the Issuer) in exchange for the Exchange Securities, the Issuer
shall mark, or caused to be marked, on the Initial Securities so exchanged that
such Initial Securities are being canceled in exchange for the Exchange
Securities; in no event shall the Initial Securities be marked as paid or
otherwise satisfied.

         (s) The Issuer Group will use its reasonable best efforts to confirm
that the Securities covered by any Registration Statement will continue to be
rated by the Credit Rating Agencies in accordance with subparagraph (cc) of
Section 4.01 of the Amended and Restated Common Security Agreement, dated as of
the date hereof, relating to the Securities.

         (t) In connection with a Shelf Registration Statement, in the event
that any broker-dealer registered under the Exchange Act shall underwrite any
Securities or participate as a member of an underwriting syndicate or selling
group or "assist in the distribution" (within the meaning of the Conduct Rules
(the "Rules") of the National Association of Securities Dealers, Inc. ("NASD"))
thereof, whether as a Holder of such Securities or as an underwriter, a
placement or sales agent or a broker or dealer in respect thereof, or otherwise,
the Issuer Group will assist such broker-dealer in complying with the
requirements of such Rules, including, without limitation, by (i) if such Rules,
including Rule 2720, shall so require, engaging a "qualified independent
underwriter" (as defined in Rule 2720) to participate in the preparation of the
Registration Statement relating to such Securities, to exercise usual standards
of due diligence in respect thereto and, if any portion of the offering
contemplated by such Registration Statement is an underwritten offering or is
made through a placement or sales agent, to recommend the yield of such
Securities, (ii) indemnifying any such qualified independent underwriter to the
extent of the indemnification of underwriters provided in Section 5 hereof and
(iii) providing such information to such broker-dealer as may be required in
order for such broker-dealer to comply with the requirements of the Rules.

         (u) The Issuer Group shall use its reasonable best efforts to take all
other steps necessary to effect the registration of the Securities covered by a
Registration Statement contemplated hereby.

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         4. Registration Expenses. The Issuer Group shall bear all fees and
expenses incurred in connection with the performance of its obligations under
Sections 1 through 3 hereof, whether or not the Registered Exchange Offer or a
Shelf Registration is filed or becomes effective, and, in the event of a Shelf
Registration, shall bear or reimburse the Holders of the Securities covered
thereby for the reasonable fees and disbursements of one firm of counsel
designated by the Holders of a majority in principal amount of the Securities
covered thereby to act as counsel for the Holders of the Securities in
connection therewith.

         5. Indemnification. (a) The Issuer Group agrees to indemnify and hold
harmless each Holder of the Securities, any Participating Broker-Dealer and each
person, if any, who controls such Holder or such Participating Broker-Dealer
within the meaning of the Securities Act or the Exchange Act (each Holder, any
Participating Broker-Dealer and such controlling persons are referred to
collectively as the "Indemnified Parties") from and against any losses, claims,
damages or liabilities, joint or several, or any actions in respect thereof
(including, but not limited to, any losses, claims, damages, liabilities or
actions relating to purchases and sales of the Securities) to which each
Indemnified Party may become subject under the Securities Act, the Exchange Act
or otherwise, insofar as such losses, claims, damages, liabilities or actions
arise out of or are based upon any untrue statement or alleged untrue statement
of a material fact contained in a Registration Statement or prospectus or in any
amendment or supplement thereto or in any preliminary prospectus relating to a
Shelf Registration, or arise out of, or are based upon, the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and shall reimburse, as
incurred, the Indemnified Parties for any legal or other expenses reasonably
incurred by them in connection with investigating or defending any such loss,
claim, damage, liability or action in respect thereof; provided, however, that
(i) the Issuer Group shall not be liable in any such case to the extent that
such loss, claim, damage or liability arises out of or is based upon any untrue
statement or alleged untrue statement or omission or alleged omission made in a
Registration Statement or prospectus or in any amendment or supplement thereto
or in any preliminary prospectus relating to a Shelf Registration in reliance
upon and in conformity with written information pertaining to such Holder and
furnished to the Issuer by or on behalf of such Holder specifically for
inclusion therein and (ii) with respect to any untrue statement or omission or
alleged untrue statement or omission made in any preliminary prospectus relating
to a Shelf Registration Statement, the indemnity agreement contained in this
subsection (a) shall not inure to the benefit of any Holder or Participating
Broker-Dealer from whom the person asserting any such losses, claims, damages or
liabilities purchased the Securities concerned, to the extent that a prospectus
relating to such Securities was required to be delivered by such Holder or
Participating Broker-Dealer under the Securities Act in connection with such
purchase and any such loss, claim, damage or liability of such Holder or
Participating Broker-Dealer results from the fact that there was not sent or
given to such person, at or prior to the written confirmation of the sale of
such Securities to such person, a copy of the final prospectus if the Issuer
Group had previously furnished copies thereof to such Holder or Participating
Broker-Dealer; provided, further, however, that this indemnity agreement

                                      -12-

<PAGE>

will be in addition to any liability which the Issuer Group may otherwise have
to such Indemnified Party. The Issuer Group shall also indemnify underwriters,
their officers and directors and each person who controls such underwriters
within the meaning of the Securities Act or the Exchange Act to the same extent
as provided above with respect to the indemnification of the Holders of the
Securities if requested by such Holders.

         (b) Each Holder of the Securities, severally and not jointly, will
indemnify and hold harmless each member of the Issuer Group and each person, if
any, who controls the Issuer Group within the meaning of the Securities Act or
the Exchange Act from and against any losses, claims, damages or liabilities or
any actions in respect thereof, to which the Issuer Group or any such
controlling person may become subject under the Securities Act, the Exchange Act
or otherwise, insofar as such losses, claims, damages, liabilities or actions
arise out of or are based upon any untrue statement or alleged untrue statement
of a material fact contained in a Registration Statement or prospectus or in any
amendment or supplement thereto or in any preliminary prospectus relating to a
Shelf Registration, or arise out of or are based upon the omission or alleged
omission to state therein a material fact necessary to make the statements
therein not misleading, but in each case only to the extent that the untrue
statement or omission or alleged untrue statement or omission was made in
reliance upon and in conformity with written information pertaining to such
Holder and furnished to the Issuer by or on behalf of such Holder specifically
for inclusion therein; and, subject to the limitation set forth immediately
preceding this clause, shall reimburse, as incurred, the Issuer Group for any
legal or other expenses reasonably incurred by the Issuer Group or any such
controlling person in connection with investigating or defending any loss,
claim, damage, liability or action in respect thereof. This indemnity agreement
will be in addition to any liability which such Holder may otherwise have to the
Issuer Group or any of its controlling persons.

         (c) Promptly after receipt by an indemnified party under this Section 5
of notice of the commencement of any action or proceeding (including a
governmental investigation), such indemnified party will, if a claim in respect
thereof is to be made against the indemnifying party under this Section 5,
notify the indemnifying party of the commencement thereof; but the omission so
to notify the indemnifying party will not, in any event, relieve the
indemnifying party from any obligations to any indemnified party other than the
indemnification obligation provided in paragraph (a) or (b) above. In case any
such action is brought against any indemnified party, and it notifies the
indemnifying party of the commencement thereof, the indemnifying party will be
entitled to participate therein and, to the extent that it may wish, jointly
with any other indemnifying party similarly notified, to assume the defense
thereof, with counsel reasonably satisfactory to such indemnified party (who
shall not, except with the consent of the indemnified party, be counsel to the
indemnifying party), and after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof the
indemnifying party will not be liable to such indemnified party under this
Section 5 for any legal or other expenses, other than reasonable costs of
investigation, subsequently incurred by such indemnified party in connection
with the defense thereof. No indemnifying party

                                      -13-

<PAGE>


shall, without the prior written consent of the indemnified party, effect any
settlement of any pending or threatened action in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party unless such settlement includes an
unconditional release of such indemnified party from all liability on any claims
that are the subject matter of such action.

         (d) If the indemnification provided for in this Section 5 is
unavailable or insufficient to hold harmless an indemnified party under
subsections (a) or (b) above, then each indemnifying party shall contribute to
the amount paid or payable by such indemnified party as a result of the losses,
claims, damages or liabilities (or actions in respect thereof) referred to in
subsection (a) or (b) above (i) in such proportion as is appropriate to reflect
the relative benefits received by the indemnifying party or parties on the one
hand and the indemnified party on the other from the exchange of the Securities,
pursuant to the Registered Exchange Offer, or (ii) if the allocation provided by
the foregoing clause (i) is not permitted by applicable law, in such proportion
as is appropriate to reflect not only the relative benefits referred to in
clause (i) above but also the relative fault of the indemnifying party or
parties on the one hand and the indemnified party on the other in connection
with the statements or omissions that resulted in such losses, claims, damages
or liabilities (or actions in respect thereof) as well as any other relevant
equitable considerations. The relative fault of the parties shall be determined
by reference to, among other things, whether the untrue or alleged untrue
statement of a material fact or the omission or alleged omission to state a
material fact relates to information supplied by the Issuer Group on the one
hand or such Holder or such other indemnified party, as the case may be, on the
other, and the parties' relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. The amount paid by
an indemnified party as a result of the losses, claims, damages or liabilities
referred to in the first sentence of this subsection (d) shall be deemed to
include any legal or other expenses reasonably incurred by such indemnified
party in connection with investigating or defending any action or claim which is
the subject of this subsection (d). Notwithstanding any other provision of this
Section 5(d), the Holders of the Securities shall not be required to contribute
any amount in excess of the amount by which the net proceeds received by such
Holders from the sale of the Securities pursuant to a Registration Statement
exceeds the amount of damages which such Holders have otherwise been required to
pay by reason of such untrue or alleged untrue statement or omission or alleged
omission. No person guilty of fraudulent misrepresentation (within the meaning
of Section 1l(f) of the Securities Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation. For purposes
of this paragraph (d), each person, if any, who controls such indemnified party
within the meaning of the Securities Act or the Exchange Act shall have the same
rights to contribution as such indemnified party and each person, if any, who
controls the Issuer Group within the meaning of the Securities Act or the
Exchange Act shall have the same rights to contribution as the Issuer Group.

         (e) The agreements contained in this Section 5 shall survive the sale
 of the Securities pursuant to a Registration Statement and shall remain in full
 force and effect,

                                      -14-

<PAGE>

regardless of any termination or cancellation of this Agreement or any
investigation made by or on behalf of any indemnified party.

         6.    Additional Interest Under Certain Circumstances. (a) Additional
interest (the "Additional Interest") with respect to the Initial Securities
shall be assessed as follows if any of the following events occur (each such
event in clauses (i) through (iii) below a "Registration Default"):

         (i)   If by 120 days following the Effective Date neither the Exchange
Offer Registration Statement nor a Shelf Registration Statement has been filed
with the Commission (or, in the case of a Shelf Registration Statement required
to be filed in response to a change in law or applicable interpretation of the
Commission staff, if later, such Shelf Registration Statement has not been filed
within 60 days after publication of the change in law or interpretation, but in
no event before 120 days after the Effective Date);

         (ii)  If by 270 days following the Effective Date neither the
Registered Exchange Offer is consummated nor, if required in lieu thereof, the
Shelf Registration Statement is declared effective by the Commission (or, in the
case of a Shelf Registration Statement required to be filed in response to a
change in law or applicable interpretation of the Commission staff, if later,
such Shelf Registration Statement has not been declared effective within 120
days after the publication of the change in law or interpretation but in no
event before 270 days after the Effective Date); or

         (iii) If after 270 days following the Effective Date the Exchange Offer
Registration Statement or, if after 120 days after a filing obligation arises in
the case of a Shelf Registration Statement as described above, the Shelf
Registration Statement is declared effective (A) such Registration Statement
thereafter ceases to be effective or (B) such Registration Statement or the
related prospectus ceases to be usable except as permitted hereby in connection
with resales of Transfer Restricted Securities during the periods specified
herein because either (1) any event occurs as a result of which the related
prospectus forming part of such Registration Statement would include any untrue
statement of a material fact or omit to state any material fact necessary to
make the statements therein in the light of the circumstances under which they
were made not misleading, or (2) it shall be necessary to amend such
Registration Statement or supplement the related prospectus, to comply with the
Securities Act or the Exchange Act or the respective rules thereunder.

Additional Interest shall accrue on the Initial Securities over and above the
interest set forth in the title of the Securities from and including the date on
which any such Registration Default shall occur to but excluding the date on
which all such Registration Defaults have been cured, at a rate of 0.50% per
annum (the "Additional Interest Rate").

Notwithstanding the foregoing, Additional Interest shall not be payable on any
Security to the extent that the Holder of such Security has failed to comply
with its obligations to furnish information pursuant to Section 3(n).

                                      -15-

<PAGE>

         (b) A Registration Default referred to in Section 6(a)(iii) hereof
shall be deemed not to have occurred and be continuing in relation to a Shelf
Registration Statement or the related prospectus if (i) such Registration
Default has occurred solely as a result of (x) the filing of a post-effective
amendment to such Shelf Registration Statement to incorporate annual audited
financial information with respect to the Issuer Group where such post-effective
amendment is not yet effective and needs to be declared effective to permit
Holders to use the related prospectus or (y) other material events (including
without limitation potential corporate transactions) with respect to the Issuer
Group that would need to be described in such Shelf Registration Statement or
the related prospectus and (ii) in the case of clause (y), the Issuer Group is
either proceeding promptly and in good faith to amend or supplement such Shelf
Registration Statement and related prospectus to describe such events or has a
bona fide business reason for delaying such amendment or supplement; provided,
however, that in any case if such Registration Default occurs for a continuous
period in excess of 30 days, Additional Interest shall be payable in accordance
with the above paragraph from the day such Registration Default occurs until
such Registration Default is cured.

         (c) Any amounts of Additional Interest due pursuant to clause (i), (ii)
or (iii) of Section 6(a) above will be payable in cash on the regular interest
payment dates with respect to the Securities. The amount of Additional Interest
will be determined by multiplying the applicable Additional Interest rate by the
principal amount of the Initial Securities to which such Registration Default
relates, multiplied by a fraction, the numerator of which is the number of days
such Additional Interest rate was applicable during such period (determined on
the basis of a 360-day year comprised of twelve 30-day months), and the
denominator of which is 360.

         (d) The Issuer Group shall notify the Capital Markets Trustee within
three business days (i) upon the occurrence of any Registration Default in
respect of which Additional Interest is required to be paid and (ii) upon any
Registration Default being cured.

         (e) "Transfer Restricted Securities" means each Security until (i) the
date on which such Security has been exchanged by a person other than a
broker-dealer for a freely transferable Exchange Security in the Registered
Exchange Offer, (ii) following the exchange by a broker-dealer in the Registered
Exchange Offer of an Initial Security for an Exchange Security, the date on
which such Exchange Security is sold to a purchaser who receives from such
broker-dealer on or prior to the date of such sale a copy of the prospectus
contained in the Exchange Offer Registration Statement, (iii) the date on which
such Security has been effectively registered under the Securities Act and
disposed of in accordance with the Shelf Registration Statement or (iv) the date
on which such Security is distributed to the public pursuant to Rule 144 under
the Securities Act or is saleable pursuant to Rule 144(k) under the Securities
Act.

         7. Rules 144 and 144A. The Issuer Group shall use its reasonable best
efforts to file the reports required to be filed by it under the Securities Act
and the Exchange Act in

                                      -16-

<PAGE>

a timely manner and, if at any time the Issuer Group is not required to file
such reports, it will, upon the request of any Holder of Securities, make
publicly available other information so long as necessary to permit sales of
their securities pursuant to Rules 144 and 144A. The Issuer Group covenants that
it will take such further action as any Holder of Securities may reasonably
request, all to the extent required from time to time to enable such Holder to
sell Securities without registration under the Securities Act within the
limitation of the exemptions provided by Rules 144 and 144A (including the
requirements of Rule 144A(d)(4)). The Issuer Group will provide a copy of this
Agreement to prospective purchasers of Initial Securities identified to the
Issuer Group by the Holders upon request. Upon the written request of any Holder
of Initial Securities prior to the filing of a Registration Statement, the
Issuer Group shall deliver to such Holder a written statement as to whether it
has complied with such requirements. Notwithstanding the foregoing, nothing in
this Section 7 shall be deemed to require the Issuer Group to register any of
its securities pursuant to the Exchange Act.

     8. Underwritten Registrations. If any of the Transfer Restricted Securities
covered by any Shelf Registration are to be sold in an underwritten offering,
the investment banker or investment bankers and manager or managers that will
administer the offering ("Managing Underwriters") will be selected by the
Holders of a majority in aggregate principal amount of such Transfer Restricted
Securities to be included in such offering.

     No person may participate in any underwritten registration hereunder unless
such person (i) agrees to sell such person's Transfer Restricted Securities on
the basis reasonably provided in any underwriting arrangements approved by the
persons entitled hereunder to approve such arrangements and (ii) completes and
executes all questionnaires, powers of attorney, indemnities, underwriting
agreements and other documents reasonably required under the terms of such
underwriting arrangements.

     9. Representations and Warranties. Each of the Issuer, the Partnership, the
Partners and PRG hereby represents and warrants to and for the benefit of the
Capital Markets Trustee and the holders of the Initial Securities from time to
time that the Exchange Securities have been duly authorized by the Borrower, the
Partnership, the Partners and PRG, and each of them has all requisite corporate
power and authority to execute, issue and deliver the Exchange Securities and to
incur and perform its obligations provided for therein. When issued in
accordance with the terms of this Agreement and the Indenture, the Exchange
Securities, at the consummation of the Exchange Offer, will have been duly
executed, authenticated, issued and delivered and will constitute valid and
binding obligations of the Borrower, the Partnership, the Partners and PRG,
entitled to the benefits provided in the Indenture and, indirectly, the security
provided in the Security Documents (as defined in the Common Security Agreement
referred to in the Indenture), and enforceable in accordance with their terms,
subject to bankruptcy, insolvency, fraudulent transfer, reorganization,
moratorium and similar laws of general applicability relating to or affecting
creditors' rights and to general equity principles.

                                      -17-

<PAGE>

     10. Miscellaneous.

     (a) Joint and Several Obligations; Guarantee. Each member of the Issuer
Group shall be jointly and severally liable for all obligations of the Issuer
Group under this Agreement.

     (b) Amendments and Waivers. The provisions of this Agreement may not be
amended, modified or supplemented, and waivers or consents to departures from
the provisions hereof may not be given, except by the Issuer with the written
consent of the Holders of a majority in principal amount of the Securities
affected by such amendment, modification, supplement, waiver or consents.

     (c) Notices. All notices and other communications provided for or permitted
hereunder shall be made in writing by hand delivery, first-class mail, facsimile
transmission, or air courier which guarantees overnight delivery:

          (1) if to a Holder of the Securities, at the most current address
given by such Holder to the Issuer.

          (2) if to the Capital Markets Trustee:

                 HSBC Bank USA,
                 as Capital Markets Trustee for the Capital Markets Senior
                 Lenders
                 Issuer Services
                 452 Fifth Avenue, New York
                 New York, NY 10018-2706
                 Fax No.: (212) 525-1300

     with a copy to:

                 Winston & Strawn
                 200 Park Avenue
                 New York, NY 10166
                 Fax No.: (212) 294-4700

          (3) if to any member of the Issuer Group, at the following address:

                 The Premcor Refining Group, Inc.
                 1700 East Putnam Avenue
                 Suite 500
                 Old Greenwich
                 Connecticut, CT 06870
                 Fax No.: (203) 637-4877

                                      -18-

<PAGE>

     with a copy to:

                 Simpson Thacher & Bartlett
                 425 Lexington Avenue
                 New York, NY 10017
                 Fax No.: (212) 455-2502

     All such notices and communications shall be deemed to have been duly
given: at the time delivered by hand, if personally delivered; three business
days after being deposited in the mail, postage prepaid, if mailed; when receipt
is acknowledged by recipient's facsimile machine operator, if sent by facsimile
transmission; and on the day delivered, if sent by overnight air courier
guaranteeing next day delivery.

     (d) No Inconsistent Agreements. No member of the Issuer Group has, as of
the date hereof, entered into, nor shall it, on or after the date hereof, enter
into, any agreement with respect to the Issuer's securities that is inconsistent
with the rights granted to the Holders herein or otherwise conflicts with the
provisions hereof.

     (e) Successors and Assigns; Benefits of Agreement. This Agreement shall be
binding upon each member of the Issuer Group and each of their respective
successors and permitted assigns. Nothing in this Agreement, express or implied,
shall give to any person, other than the parties hereto, the Holders and their
respective successors and permitted assigns hereunder any benefit or any legal
or equitable right or remedy.

     (f) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

     (g) Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

     (h) Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

     (i) Severability. If any one or more of the provisions contained herein, or
the application thereof in any circumstance, is held invalid, illegal or
unenforceable, the validity, legality and enforceability of any such provision
in every other respect and of the remaining provisions contained herein shall
not be affected or impaired thereby.

     (j) Securities Held by the Issuer Group. Whenever the consent or approval
of Holders of a specified percentage of principal amount of Securities is
required hereunder, Securities held by any member of the Issuer Group or their
respective affiliates (other than subsequent Holders of Securities if such
subsequent Holders are deemed to be affiliates solely by reason of their
holdings of such Securities) shall not be counted in

                                      -19-

<PAGE>

determining whether such consent or approval was given by the Holders of such
required percentage.

       (k) Agent for Service; Submission to Jurisdiction; Waiver of Immunities.
By the execution and delivery of this Agreement, each member of the Issuer Group
(i) acknowledges that it has, by separate written instrument, irrevocably
designated and appointed CT Corporation System and any successor entity), as its
authorized agent upon which process may be served in any suit or proceeding
arising out of or relating to this Agreement that may be instituted in any
federal or state court in the State of New York or brought under federal or
state securities laws, and acknowledges that CT Corporation System has accepted
such designation, (ii) submits to the nonexclusive jurisdiction of any such
court in any such suit or proceeding, and (iii) agrees that service of process
upon CT Corporation System and written notice of said service to the Issuer
Group shall be deemed in every respect effective service of process upon it in
any such suit or proceeding. Each member of the Issuer Group further agrees to
take any and all action, including the execution and filing of any and all such
documents and instruments, as may be necessary to continue such designation and
appointment of CT Corporation System in full force and effect so long as any of
the Securities shall be outstanding. To the extent that any member of the Issuer
Group may acquire any immunity from jurisdiction of any court or from any legal
process (whether through service of notice, attachment prior to judgment,
attachment in aid of execution, execution or otherwise) with respect to itself
or its property, it hereby irrevocably waives such immunity in respect of this
Agreement, to the fullest extent permitted by law.

       (1) Effectiveness. This Agreement shall come into full force and effect
upon the satisfaction or waiver of all conditions precedent set forth in Section
4.02 of the Master Amendment Agreement, dated as of the date hereof, among the
Issuer, the Partnership, the Partners, PRG, Premcor USA Inc., Premcor Inc.,
Deutsche Bank Trust Company Americas, as Collateral Trustee for the Senior
Lenders, and HSBC Bank USA, as Capital Markets Trustee for the Capital Markets
Senior Lenders, in accordance with the terms thereof.

                                      -20-

<PAGE>

       If the foregoing is in accordance with your understanding of our
agreement, please sign and return to the Issuer a counterpart hereof, whereupon
this instrument, along with all counterparts, will become a binding agreement
among the Capital Markets Trustee on behalf of the Holders and the Issuer Group
in accordance with its terms.

                                        Very truly yours,

                                        Port Arthur Finance Corp.

                                        By:_____________________________________
                                           Name:
                                           Title:

                                        Port Arthur Coker Company L.P.
                                        By: Sabine River Holding Corp.

                                        By:_____________________________________
                                           Name:
                                           Title:

                                        Sabine River Holding Corp.

                                        By:_____________________________________
                                           Name:
                                           Title:

                                        Neches River Holding Corp.

                                        By:_____________________________________
                                           Name:
                                           Title:

                                        THE PREMCOR REFINING GROUP INC.

                                        By:_____________________________________
                                           Name:
                                           Title:

                                      -21-

<PAGE>

The foregoing Registration
Rights Agreement is hereby confirmed
and accepted as of the date first
above written.


HSBC BANK USA,
as Capital Markets Trustee for the Capital Markets Senior Lenders

       By:______________________
          Name:
          Title:

                                      -22-

<PAGE>


                                     ANNEX A

         Each broker-dealer that receives Exchange Securities for its own
account pursuant to the Exchange Offer must acknowledge that it will deliver a
prospectus in connection with any resale of such Exchange Securities. The Letter
of Transmittal states that by so acknowledging and by delivering a prospectus, a
broker-dealer will not be deemed to admit that it is an "underwriter" within the
meaning of the Securities Act. This Prospectus, as it may be amended or
supplemented from time to time, may be used by a broker-dealer in connection
with resales of Exchange Securities received in exchange for Initial Securities
where such Initial Securities were acquired by such broker-dealer as a result of
market-making activities or other trading activities. The Issuer Group has
agreed that, for a period of 120 days after the Expiration Date (as defined
herein), it will make this Prospectus available to any broker-dealer for use in
connection with any such resale. See "Plan of Distribution."

                                       23

<PAGE>

                                     ANNEX B

         Each broker-dealer that receives Exchange Securities for its own
account in exchange for Initial Securities, where such Initial Securities were
acquired by such broker-dealer as a result of market-making activities or other
trading activities, must acknowledge that it will deliver a prospectus in
connection with any resale of such Exchange Securities. See "Plan of
Distribution."

                                       24

<PAGE>

                                     ANNEX C
                              PLAN OF DISTRIBUTION

         Each broker-dealer that receives Exchange Securities for its own
account pursuant to the Exchange Offer must acknowledge that it will deliver a
prospectus in connection with any resale of such Exchange Securities. This
Prospectus, as it may be amended or supplemented from time to time, may be used
by a broker-dealer in connection with resales of Exchange Securities received in
exchange for Initial Securities where such Initial Securities were acquired as a
result of market-making activities or other trading activities. The Issuer Group
has agreed that, for a period of 120 days after the Expiration Date, it will
make this prospectus, as amended or supplemented, available to any broker-dealer
for use in connection with any such resale. In addition, dealers effecting
transactions in the Exchange Securities may be required to deliver a prospectus.

         The Issuer Group will not receive any proceeds from any sale of
Exchange Securities by broker-dealers. Exchange Securities received by
broker-dealers for their own account pursuant to the Exchange Offer may be sold
from time to time in one or more transactions in the over-the-counter market, in
negotiated transactions, through the writing of options on the Exchange
Securities or a combination of such methods of resale, at market prices
prevailing at the time of resale, at prices related to such prevailing market
prices or negotiated prices. Any such resale may be made directly to purchasers
or to or through brokers or dealers who may receive compensation in the form of
commissions or concessions from any such broker-dealer or the purchasers of any
such Exchange Securities. Any broker-dealer that resells Exchange Securities
that were received by it for its own account pursuant to the Exchange Offer and
any broker or dealer that participates in a distribution of such Exchange
Securities may be deemed to be an "underwriter" within the meaning of the
Securities Act and any profit on any such resale of Exchange Securities and any
commission or concessions received by any such persons may be deemed to be
underwriting compensation under the Securities Act. The Letter of Transmittal
states that, by acknowledging that it will deliver and by delivering a
prospectus, a broker-dealer will not be deemed to admit that it is an
"underwriter" within the meaning of the Securities Act.

         For a period of 120 days after the Expiration Date the Issuer Group
will promptly send additional copies of this Prospectus and any amendment or
supplement to this Prospectus to any broker-dealer that requests such documents
in the Letter of Transmittal. The Issuer Group has agreed to pay all expenses
incident to the Exchange Offer (including the expenses of one counsel for the
Holders of the Securities) other than commissions or concessions of any brokers
or dealers and will indemnify the Holders of the Securities (including any
broker-dealers) against certain liabilities, including liabilities under the
Securities Act.

                                       25

<PAGE>

                                     ANNEX D

[_]  CHECK HERE IF YOU ARE A BROKER-DEALER AND WISH TO RECEIVE 10 ADDITIONAL
COPIES OF THE PROSPECTUS AND 10 COPIES OF ANY AMENDMENTS OR SUPPLEMENTS THERETO.

                 Name:___________________________________________
                 Address:________________________________________
                        _________________________________________



         If the undersigned is not a broker-dealer, the undersigned represents
that it is not engaged in, and does not intend to engage in, a distribution of
Exchange Securities. If the undersigned is a broker-dealer that will receive
Exchange Securities for its own account in exchange for Initial Securities that
were acquired as a result of market-making activities or other trading
activities, it acknowledges that it will deliver a prospectus in connection with
any resale of such Exchange Securities; however, by so acknowledging and by
delivering a prospectus, the undersigned will not be deemed to admit that it is
an "underwriter" within the meaning of the Securities Act.

                                       26