<PAGE>

                                                                    Exhibit 10.4

                              AMENDED AND RESTATED
                              EMPLOYMENT AGREEMENT

          AMENDED AND RESTATED EMPLOYMENT AGREEMENT (the "Agreement") effective
June 1, 2002 by and between Premcor Inc. (the "Company") and Henry Kuchta (the
"Executive").

          WHEREAS, Executive became the Executive Vice-President-Refining of the
Company on April 26, 2002 and on that date the Executive and the Company entered
into an Employment Agreement; and

          WHEREAS, Executive and the Company desire to amend and restate that
agreement in its entirely.

          1. Term of Employment. Subject to the provisions of Section 8,
Executive shall be employed by the Company for a period commencing on June 1,
2002 ("Start Date") and ending on June 1, 2004 (the "Employment Term") on the
terms and subject to the conditions set forth in this Agreement; provided,
however, that commencing with June 1, 2004 and on each June 1 thereafter (each
an "Extension Date"), the Employment Term shall be automatically extended for an
additional one-year period, unless the Company or Executive provides the other
party hereto not less than 60 days prior written notice before the next
Extension Date that the Employment Term shall not be so extended.

          2. Position.

               a. During the Employment Term, Executive shall serve as the
Executive Vice President-Refining of the Company. In such position, Executive
shall have such duties and authority as shall be determined from time to time by
the Chief Executive Officer and/or Board of Directors of the Company (the
"Board").

               b. During the Employment Term, Executive shall devote Executive's
full business time and best efforts to the performance of Executive's duties
hereunder and shall not engage in any other business, profession or occupation
for compensation or otherwise which would conflict or interfere with the
rendition of such services either directly or indirectly, without the prior
written consent of the Board; provided that nothing herein shall preclude
Executive (i) from continuing to serve on any board of directors or trustees of
any business corporation or any charitable organization and (ii) subject to the
prior written approval of the Board, which approval shall not be unreasonably
withheld, from accepting appointment to any board of directors or trustees of
any business corporation or any charitable organization; provided in each case,
and in the aggregate, that such activities do not materially conflict or
interfere with the performance of Executive's duties hereunder or conflict with
Section 9.

          3. Base Salary. During the Employment Term, the Company shall pay
Executive a base salary at the annual rate of $250,000, payable in regular
installments in accordance with the Company's usual payment practices. Executive
shall be entitled to such increases in Executive's base salary, if any, as may
be determined from time to time in the sole discretion of the Board. Executive's
annual rate of base salary, as in effect from time to time, is hereinafter
referred to as the "Base Salary."

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                                                                               2

          4. Annual Bonus. With respect to each fiscal year of the Company
ending during the Employment Term, Executive shall be eligible to earn an annual
bonus award (an "Annual Bonus") if net earnings per share to common shareholders
of the Company, calculated on a fully diluted basis and according to GAAP, as
determined by the Company's outside auditors, excluding the after-tax impact of
any extraordinary or special items that the Board determines in good faith are
not appropriately includable in the Annual Bonus calculation because such items
do not accurately reflect the operating performance of the Company, such as
inventory write ups and write downs, LIFO adjustments, asset purchase or
sale-related gains or losses and acquisition-related write downs ("Adjusted
EPS"), is at least equal to $2.50. Upon achievement of an Adjusted EPS of $2.50,
the Annual Bonus shall equal fifty percent (50%) of his Base Salary (the "Base
Bonus"). For each $0.01 increase in the applicable fiscal year's Adjusted EPS
above $2.50, the Annual Bonus shall be increased by an amount equal to one
percent of Executive's Base Salary, provided that in no event shall the Annual
Bonus be greater than three times Executive's Base Salary. The Annual Bonus
shall be paid to Executive within fifteen business days after the outside
auditors approve the Company's year-end earnings release. The Annual Bonus for
2002 shall be calculated based on earnings from January 1, 2002, and the
resulting amount multiplied by 9/12ths, to arrive at the amount due for the nine
months of 2002, so long as Executive is employed hereunder as of December 31,
2002. Annual Bonuses for subsequent full years during which Executive is
employed hereunder will reflect the full year (January 1 through December 31).

          5. Equity Arrangements. During the month of January in each of the
years 2003 and 2004, Executive shall receive a grant of options to purchase
25,000 shares of Company common stock at an exercise price per share equal to
Fair Market Value (as defined in the Plan) on the date of grant (the "Annual
Options"). Subject to Executive's continued employment with the Company, such
Annual Options will vest in equal installments on each of the first three
anniversaries of the date of grant, and will become fully vested upon the
occurrence of a Change in Control of the Company. Other terms and conditions of
the Annual Options shall be as set forth herein, in the Plan and an option
agreement between the Company and Executive. If the Company should, prior to any
Annual Option grant, be involved in any merger, reorganization, stock split or
spinoff or other similar event, the number of shares subject to the Annual
Options yet to be granted, as provided above, shall be adjusted on a pro rata
basis.

          6. Employee Benefits. During the Employment Term, Executive shall be
entitled to participate in the Company's employee benefit plans (which term does
not include bonus or incentive compensation plans), other than any non-qualified
pension plan or any severance pay plan, as in effect from time to time
(collectively "Employee Benefits"), on the same basis as those benefits are
generally made available to other senior executives of the Company. Executive
shall also be entitled to participant in the Premcor Senior Executive Retirement
Plan as approved by the Board of Directors of the Company on April 2, 2002.

          7. Business Expenses. During the Employment Term, reasonable business
expenses incurred by Executive in the performance of Executive's duties
hereunder shall be reimbursed by the Company following presentation by Executive
of proof of such expenses, as and when reasonably required by the Company.

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                                                                               3

          8. Termination. The Employment Term and Executive's employment
hereunder may be terminated by the Company at any time and for any reason or by
Executive for Good Reason. Notwithstanding any other provision of this Agreement
(other than Section 13(h)), the provisions of this Section 8 shall exclusively
govern Executive's rights upon termination of employment with the Company and
its affiliates.

               a. By the Company For Cause or By Executive Resignation Without
Good Reason.

            (i)  If Executive's employment is terminated by the Company for
Cause, or if Executive resigns without Good Reason, Executive shall be entitled
to receive:

               (A) the Base Salary through the date of termination;

               (B) any Annual Bonus earned but unpaid as of the date of
     termination for any previously completed fiscal year (including, if
     applicable, 2002);

               (C) reimbursement for any unreimbursed business expenses properly
     incurred by Executive in accordance with this Agreement prior to the date
     of Executive's termination;

               (D) such Employee Benefits, if any, as to which Executive may be
     entitled under the employee benefit plans of the Company (the amounts
     described in clauses (A) through (D) hereof being referred to as the
     "Accrued Rights"); and

               (E) any vested benefits as provided pursuant to the Premcor
     Senior Executive Retirement Plan, accrued in respect to any prior fiscal
     year.

          Following such termination of Executive's employment by the Company
for Cause or resignation by Executive without Good Reason, except as set forth
in this Section 8(a)(i), in the Plan and any applicable option agreement,
Executive shall have no further rights to any compensation or any other benefits
under this Agreement.

            (ii) For purposes of this Agreement, "Cause" shall mean (A)
Executive's continued failure substantially to perform Executive's duties
hereunder (other than as a result of total or partial incapacity due to physical
or mental illness) for a period of 20 days following written notice by the
Company to Executive of such failure, (B) Executive's conviction of, or plea of
nolo contendere to a crime constituting (x) a felony under the laws of the
United States or any state thereof or (y) a misdemeanor involving moral
turpitude, (C) Executive's willful malfeasance or willful misconduct in
connection with Executive's duties hereunder or any act or omission which is
injurious to the financial condition or business reputation of the Company or
any of its subsidiaries or affiliates, other than an act or omission that was
committed or omitted by Executive in the good faith belief that it was in the
best interest of the Company or (D) Executive's breach of the provisions of
Sections 9 or 10 of this Agreement.

               b. Disability or Death.

            (i)  The Employment Term and Executive's employment hereunder shall
terminate upon Executive's death and may be terminated by the Company if
Executive becomes physically or mentally incapacitated and is therefore unable
for a period of six (6) consecutive

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                                                                               4

months or for an aggregate of nine (9) months in any twenty-four (24)
consecutive month period to perform Executive's duties (such incapacity is
hereinafter referred to as "Disability"). Any question as to the existence of
the Disability of Executive as to which Executive and the Company cannot agree
shall be determined in writing by a qualified independent physician mutually
acceptable to Executive and the Company. If Executive and the Company cannot
agree as to a qualified independent physician, each shall appoint such a
physician and those two physicians shall select a third who shall make such
determination in writing. The determination of Disability made in writing to the
Company and Executive shall be final and conclusive for all purposes of the
Agreement.

            (ii) Upon termination of Executive's employment hereunder for either
Disability or death, Executive or Executive's estate (as the case may be) shall
be entitled to receive:

               (A) the Accrued Rights;

               (B) a pro rata portion of any Annual Bonus, if any, that
     Executive would have been entitled to receive pursuant to Section 4 hereof
     in such year based upon the percentage of the fiscal year that shall have
     elapsed through the date of Executive's termination of employment, payable
     when such Annual Bonus would have otherwise been payable had Executive's
     employment not terminated; and

               (C) any vested benefits as provided in the Premcor Senior
     Executive Retirement Plan, accrued to the date of termination of
     employment.

          Following Executive's termination of employment due to death or
Disability, except as set forth in this Section 8(b)(ii), in the Plan and any
applicable option agreement, Executive shall have no further rights to any
compensation or any other benefits under this Agreement.

               c. By the Company Without Cause or Resignation by Executive for
Good Reason.

            (i) If Executive's employment is terminated by the Company without
Cause (other than by reason of death or Disability) or if Executive resigns for
Good Reason, Executive shall be entitled to receive:

               (A) the Accrued Rights;

               (B) subject to Executive's continued compliance with the
     provisions of Sections 9 and 10, payment, within 60 days of the date of
     termination of Executive's employment, of a lump sum equal to three times
     the sum of Executive's Base Salary and Base Bonus; and

               (C) the benefits as provided in the Premcor Senior Executive
     Retirement Plan, whether or not previously vested.

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                                                                               5

          Following Executive's termination of employment by the Company without
Cause (other than by reason of Executive's death or Disability) or by
Executive's resignation for Good Reason, except as set forth in this Section
8(c)(i), and the Plan and any applicable option agreement, Executive shall have
no further rights to any compensation or any other benefits under this
Agreement.

            (ii) For purposes of this Agreement, "Good Reason" shall mean,
without Executive's consent, (A) the failure of the Company to pay or cause to
be paid Executive's Base Salary or Annual Bonus, when due hereunder, (B) any
substantial and sustained diminution in Executive's authority or
responsibilities from those described in Section 2 hereof or (C) relocation of
Executive's principal place of business by more than 30 miles, provided that
relocation to St. Louis, MO or Greenwich, CT shall not constitute Good Reason;
provided that the events described in clauses (A), (B) and (C) of this Section
8(c)(ii) shall constitute Good Reason only if the Company fails to cure such
event within 20 days after receipt from Executive of written notice of the event
which constitutes Good Reason; provided, further, that "Good Reason" shall cease
to exist for an event on the 90th day following the later of its occurrence or
Executive's knowledge thereof, unless Executive has given the Company written
notice thereof prior to such date.

               d. Expiration of Employment Term.

            (i)  Election Not to Extend the Employment Term. In the event either
party elects not to extend the Employment Term pursuant to Section 1, unless
Executive's employment is earlier terminated pursuant to paragraphs (a), (b) or
(c) of this Section 8, Executive's termination of employment hereunder (whether
or not Executive continues as an employee of the Company thereafter) shall be
deemed to occur on the close of business on the day immediately preceding the
next scheduled Extension Date. If Executive provides the Company notice of
non-extension of the Employment Term pursuant to Section 1, Executive shall be
entitled to receive the Accrued Rights. If the Company provides Executive notice
of non-extension of the Employment Term pursuant to Section 1, Executive shall
be entitled to receive the benefits provided in Sections 8(c)(i)(A) - (C),
above.

          Following such termination of Executive's employment hereunder as a
result either party's election not to extend the Employment Term, except as set
forth in this Section 8(d)(i), Executive shall have no further rights to any
compensation or any other benefits under this Agreement.

               e. Notice of Termination. Any purported termination of employment
by the Company or by Executive (other than due to Executive's death) shall be
communicated by written Notice of Termination to the other party hereto in
accordance with Section 13(g) hereof. For purposes of this Agreement, a "Notice
of Termination" shall mean a notice which shall indicate the specific
termination provision in this Agreement relied upon and shall set forth in
reasonable detail the facts and circumstances claimed to provide a basis for
termination of employment under the provision so indicated.

               f. Board/Committee Resignation. Upon termination of Executive's
employment for any reason, Executive agrees to resign, as of the date of such
termination and to the extent applicable, from the Board (and any committees
thereof) and the Board of Directors (and any committees thereof) of any of the
Company's affiliates.

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          9. Non-Solicitation; Non-Competition.

               a. Executive acknowledges and recognizes the highly competitive
nature of the businesses of the Company and its affiliates and accordingly
agrees as follows:

     (1)           While Executive is employed by the Company and for six months
followingthe date Executive ceases to be employed by the Company (the
"Restricted Period"), Executive shall not, whether on Executive's own behalf or
on behalf of or in conjunction with any person, company, business entity or
other organization whatsoever, directly or indirectly

               (i)   solicit, or assist in soliciting, in competition with the
                     Company, the potential acquisition of refining assets in
                     the United States;

               (ii)  solicit or encourage any employee of the Company or its
                     affiliates to leave the employment of the Company or its
                     affiliates;

               (iii) hire any such person who was employed by the Company or its
                     affiliates as of the date of Executive's termination of
                     employment with the Company or whose employment with the
                     Company terminated within six months prior to the date of
                     such hire (other than any such person whose employment was
                     terminated by the Company without cause); or

               (iv)  solicit or encourage to cease to work with the Company or
                     its affiliates any consultant then under contract with the
                     Company or its affiliates.

     (2)           While Executive is employed by the Company and, following
termination of employment by the Company for Cause or by Executive without Good
Reason, for the remainder of the Employment Term (without regard to Executive's
termination of employment), Executive shall not directly or indirectly:

               (i)   engage in the business of petroleum refining or oil product
                     wholesaling in the United States

               (ii)  engage in any other business in which the Company or its
                     affiliates is engaged at the time of the termination of
                     Executive's employment, provided such other business is
                     contributing more than 10% of the Company's consolidated
                     annual revenues or net income at the time of the
                     termination of Executive's employment (any of the
                     businesses described in the preceding subparagraph (i) and
                     this subparagraph (ii) being referred to as a "Competitive
                     Business");

               (iii) enter the employ of, or render any services to, any entity
                     (or any division, affiliate, business unit or segment of
                     any entity) which engages in a Competitive Business;
                     provided that, notwithstanding the foregoing, it shall not
                     be a breach of Section 9(a)(2) for Executive to provide
                     services to any division, affiliate, business unit or
                     segment of any entity so long as (x) such division,
                     affiliate, business unit or segment does not itself engage
                     in a Competitive Business and (y) Executive does not,
                     directly or

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                                                                               7

                     indirectly, provide services or advice to any division,
                     affiliate, business unit or segment of the entity that does
                     engage in a Competitive Business;

               (iv)  acquire a financial interest in (other than a passive
                     investment acquired through a hedge fund or similar
                     vehicle), or otherwise become actively involved with, any
                     Competitive Business, directly or indirectly, as an
                     individual, partner, shareholder, officer, director,
                     principal, agent, trustee or consultant; or

               (v)   interfere with, or attempt to interfere with, business
                     relationships (whether formed before, on or after the date
                     of this Agreement) between the Company or any of its
                     affiliates and their customers, clients or suppliers in
                     connection with or on behalf of a Competitive Business.

     (3)           Notwithstanding anything to the contrary in this Agreement,
Executive may, directly or indirectly own, solely as an investment, securities
of any person engaged in the business of the Company or its affiliates which are
publicly traded on a national or regional stock exchange or on the
over-the-counter market if Executive (i) is not a controlling person of, or a
member of a group which controls, such person and (ii) does not, directly or
indirectly, own 5% or more of any class of securities of such person.

               b. It is expressly understood and agreed that although Executive
and the Company consider the restrictions contained in this Section 9 to be
reasonable, if a final judicial determination is made by a court of competent
jurisdiction that the time or territory or any other restriction contained in
this Agreement is an unenforceable restriction against Executive, the provisions
of this Agreement shall not be rendered void but shall be deemed amended to
apply as to such maximum time and territory and to such maximum extent as such
court may judicially determine or indicate to be enforceable. Alternatively, if
any court of competent jurisdiction finds that any restriction contained in this
Agreement is unenforceable, and such restriction cannot be amended so as to make
it enforceable, such finding shall not affect the enforceability of any of the
other restrictions contained herein.

          10. Confidentiality. Executive agrees to hold all Company information
confidential ("Confidential Information") and shall not at any time disclose,
retain, or use such Confidential Information for Executive's own benefit or the
benefit of any other person, without the written authorization of the Board;
provided that the foregoing shall not apply to the extent that information is
required to be disclosed by law. Executive agrees that upon termination of
Executive's employment with the Company for any reason, he shall return to the
Company immediately all Confidential Information and all copies thereof or
therefrom, in any way relating to the business of the Company.

          11. Specific Performance. Executive acknowledges and agrees that the
Company's remedies at law for a breach or threatened breach of any of the
provisions of Section 9 or Section 10 would be inadequate and the Company would
suffer irreparable damages as a result of such breach or threatened breach. In
recognition of this fact, Executive agrees that, in the event of such a breach
or threatened breach, in addition to any remedies at law, the Company, without
posting any bond, shall be entitled to cease making any payments or providing
any benefit otherwise required by this Agreement and obtain equitable relief in
the form of specific

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                                                                               8

performance, temporary restraining order, temporary or permanent injunction or
any other equitable remedy which may then be available.

          12. Gross-Up Payment.

               a. If it shall be determined that any amount, right or benefit
paid, distributed or treated as paid or distributed by the Company or any of its
affiliates to or for Executive's benefit (other than any amounts payable
pursuant to this Section 12) (a "Payment") would be subject to the excise tax
imposed by Section 4999 of the Internal Revenue Code of 1986 (the "Code"), or
any interest or penalties are incurred by Executive with respect to such excise
tax (such excise tax, together with any such interest and penalties,
collectively, the "Excise Tax"), then Executive shall be entitled to receive an
additional payment (a "Gross-Up Payment") in an amount equal to the amount
necessary such that after payment by Executive of all federal, state and local
taxes (including any interest or penalties imposed with respect to such taxes),
including, without limitation, any income taxes (and any interest and penalties
imposed with respect thereto) and Excise Tax imposed upon the Gross-Up Payment,
Executive retains an amount of the Gross-Up Payment equal to the Excise Tax
imposed upon the Payments.

               b. All determinations required to be made under this Section 12,
including whether and when a Gross-Up Payment is required, the amount of such
Gross-Up Payment and the assumptions to be utilized in arriving at such
determination, shall be made by the Company's independent auditors (the
"Auditor"). The Auditor shall provide detailed supporting calculations to both
the Company and Executive within 15 business days of the receipt of notice from
Executive or the Company that there has been a Payment, or such earlier time as
is requested by the Company. All fees and expenses of the Auditor shall be paid
by the Company. Any Gross-Up Payment, as determined pursuant to this Section 12,
shall be paid by the Company to Executive (or to the Internal Revenue Service or
other applicable taxing authority on Executive's behalf) within 5 days of the
receipt of the Auditor's determination. All determinations made by the Auditor
shall be binding upon the Company and Executive; provided that following any
payment of a Gross-Up Payment to Executive (or to the Internal Revenue Service
or other applicable taxing authority on Executive's behalf), the Company may
require Executive to sue for a refund of all or any portion of the Excise Taxes
paid on Executive's behalf, in which event the provisions of Section 12(c) below
shall apply. As a result of uncertainty regarding the application of Section
4999 of the Code hereunder, it is possible that the Internal Revenue Service may
assert that Excise Taxes are due that were not included in the Auditor's
calculation of the Gross-Up Payments (an Underpayment"). In the event that the
Company exhausts its remedies pursuant to this Section 12 and Executive
thereafter is required to make a payment of any Excise Tax, the Auditor shall
determine the amount of the Underpayment that has occurred and any additional
Gross-Up Payments that are due as a result thereof shall be promptly paid by the
Company to Executive (or to the Internal Revenue Service or other applicable
taxing authority on Executive's behalf).

               c. Executive shall notify the Company in writing of any claim
that, if successful, would require the payment by the Company of the Gross-Up
Payment. Such notification shall be given as soon as practicable but no later
than 10 business days after Executive receives written notification of such
claim and shall apprise the Company of the nature of such claim and the date on
which such claim is requested to be paid. Executive shall not pay such claim
prior to the expiration of the 30 day period following the date on which it
gives such notice to the Company) (or such shorter period ending on the date
that any payment of taxes with

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                                                                               9

respect to such claim is due). If the Company notifies Executive in writing
prior to the expiration of such period that it desires to contest such claim,
Executive shall: (i) give the Company all information reasonably requested by
the Company relating to such claim; (ii) take such action in connection with
contesting such claim as the Company shall reasonably request in writing from
time to time, including, without limitation, accepting legal representation with
respect to such claim by an attorney reasonably selected by the Company and
ceasing all efforts to contest such claim; (iii) cooperate with the Company in
good faith in order to effectively contest such claim; and (iv) permit the
Company to participate in any proceeding relating to such claim; provided,
however, that the Company shall bear and pay directly all reasonable costs and
expenses (including additional interest and penalties) incurred in connection
with such contest and shall indemnify and hold the Executive harmless, on an
after-tax basis, from any Excise Tax or income tax (including interest and
penalties with respect thereto) imposed as a result of such representation and
payment of costs and expense. Without limiting the foregoing provisions of this
Section 12, the Company shall control all proceedings taken in connection with
such contest and, at its sole option, may pursue or forego any and all
administrative appeals, proceedings, hearings and conferences with the taxing
authority in respect of such claim and may, at its sole option, either direct
Executive to pay the tax claimed and sue for a refund or contest the claim in
any permissible manner, and Executive agrees to prosecute such contest to a
determination before any administrative tribunal, in a court of initial
jurisdiction and in one or more appellate courts, as the Company shall determine
and direct; provided, however that if the Company directs the Executive to pay
such claim and sue for a refund, the Company shall advance the amount of such
payment to the Executive, on an interest-free basis, and shall indemnify and
hold the Executive harmless, on an after-tax basis, from any Excise Tax or
income tax (including interest or penalties with respect thereto) imposed with
respect to such advance or with respect to any imputed income with respect to
such advance; and further provided that any extension of the statute of
limitations relating to payment of taxes for Executive's taxable year with
respect to which such contested amount is claimed to be due is limited solely to
such contested amount. Furthermore, the Company's control of the contest shall
be limited to issues with respect to which a Gross-Up Payment would be payable
hereunder and the Executive shall be entitled to settle or contest, as the case
may be, any other issue raised by the Internal Revenue Service or any other
taxing authority.

               d. If, after the Executive's receipt of an amount advanced by the
Company pursuant to this Section 12, the Executive becomes entitled to receive
any refund with respect to such claim, the Executive shall promptly pay to the
Company the amount of such refund (together with any interest paid or credited
thereon after taxes applicable thereto). If, after the Executive's receipt of an
amount advanced by the Company pursuant to this Section 12, a determination is
made that the Executive shall not be entitled to any refund with respect to such
claim and the Company does not notify the Executive in writing of its intent to
contest such denial of refund prior to the expiration of 30 days after the
Company's receipt of notice of such determination, then such advance shall be
forgiven and shall not be required to be repaid and the amount of such advance
shall offset, to the extent thereof, the amount of Gross-Up Payment required to
be paid.

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                                                                              10

          13. Miscellaneous.

               a. Governing Law; Jurisdiction. This Agreement shall be governed
by and construed in accordance with the laws of the State of New York, without
regard to conflicts of laws principles thereof. Any suit, action or proceeding
related to this Agreement, or any judgment entered by any court related to this
Agreement, may be brought only in any court of competent jurisdiction in the
State of New York, and the parties hereby submit to the exclusive jurisdiction
of such courts. The parties (and any affiliates of the Company or beneficiary or
permitted transferee of Executive) irrevocably waive any objections which they
may now or hereafter have to the laying of venue of any suit, action or
proceeding brought in any court of competent jurisdiction in the State of New
York, and hereby irrevocably waive any claim that any such action, suit or
proceeding has been brought in an inconvenient forum.

               b. Entire Agreement; Amendments. This Agreement contains the
entire understanding of the parties with respect to the matters herein
(including, without limitation, Executive's compensation, benefits and
severance). There are no restrictions, agreements, promises, warranties,
covenants or undertakings between the parties with respect to the subject matter
herein other than those expressly set forth herein. This Agreement may not be
altered, modified, or amended except by written instrument signed by the parties
hereto.

               c. No Waiver. The failure of a party to insist upon strict
adherence to any term of this Agreement on any occasion shall not be considered
a waiver of such party's rights or deprive such party of the right thereafter to
insist upon strict adherence to that term or any other term of this Agreement.

               d. Severability. In the event that any one or more of the
provisions of this Agreement shall be or become invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions of this Agreement shall not be affected thereby.

               e. Assignment. This Agreement shall not be assignable by
Executive. This Agreement may be assigned by the Company, with Executive's
consent, such consent not to be unreasonably withheld, to a person or entity
that is a successor in interest to substantially all of the business operations
of the Company. Upon such assignment, the rights and obligations of the Company
hereunder shall become the rights and obligations of such affiliate or successor
person or entity.

               f. Successors; Binding Agreement. This Agreement shall inure to
the benefit of and be binding upon personal or legal representatives, executors,
administrators, successors, heirs, distributes, devises and legatees of the
Executive.

               g. Notice. For the purpose of this Agreement, notices and all
other communications provided for in the Agreement shall be in writing and shall
be deemed to have been duly given when delivered by hand or overnight courier or
five days after it has been mailed by United States registered mail, return
receipt requested, postage prepaid, addressed to the respective addresses set
forth below Agreement, or to such other address as either party may have
furnished to the other in writing in accordance herewith, except that notice of
change of address shall be effective only upon receipt.

<PAGE>

                                                                              11

            If to the Company:

            Premcor Inc.
            8182 Maryland Avenue
            Suite 600
            St. Louis, MO  63105
            Attention:  General Counsel

            With a copy to:

            The Blackstone Group, L.P.
            345 Park Avenue
            New York, NY  10154
            Attention:  Robert L. Friedman

            If to Executive:

            Henry Kuchta
            6 Hussars Camp Place
            Ridgefield, CT 06877

               h. Release. As a condition of receipt of the benefits described
in Section 8, Executive will be required to enter into a full and complete
release of the Company from any and all claims which Executive may then have for
whatever reason or cause in connection with Executive's employment and the
termination thereof (including, without limitation, any rights under an
employment agreement which may then be in effect), other than those obligations
specifically set out in this Agreement, the Plan, indemnification provisions in
the Company's by-laws and obligations of the Company to the extent that the
documents providing for such obligations specifically provide that the
obligations are in addition to obligations under this Agreement.

               i. Disputes. Any dispute with regard to the enforcement of this
Agreement or any matter relating to the employment of Executive by the Company
including but not limited to disputes relating to claims of employment
discrimination, alleged torts or any violation of law other than the seeking of
equitable relief in accordance with applicable law under Section 11 hereof,
shall be exclusively resolved by a single experienced arbitrator licensed to
practice law in New York, selected in accordance with the American Arbitration
Association rules and procedures, at an arbitration to be conducted in New York
City pursuant to the National Rules for the Resolution of Employment Disputes
rules of the American Arbitration Association ("AAA") with the arbitrator
applying the substantive law of the State of New York as provided for under
Section 13(a) hereof. The AAA shall provide the parties hereto with lists for
the selection of arbitrators composed entirely of arbitrators who are members of
the National Academy of Arbitrators and who have prior experience in the
arbitration of disputes between employers and senior executives. The
determination of the arbitrator shall be final and binding on the parties hereto
and judgment therein may be entered in any court of competent jurisdiction in
accordance with Section 13(a). Each party shall pay its own attorneys fees and
disbursements and other costs of the arbitration.

<PAGE>

                                                                              12

               j. Executive Representation. Executive hereby represents to the
Company that the execution and delivery of this Agreement by Executive and the
Company and the performance by Executive of Executive's duties hereunder shall
not constitute a breach of, or otherwise contravene, the terms of any employment
agreement or other agreement or policy to which Executive is a party or
otherwise bound.

               k. Cooperation. Executive shall provide his reasonable
cooperation in connection with any action or proceeding (or any appeal from any
action or proceeding) that relates to events occurring during Executive's
employment hereunder. The Company shall provide Executive with a reasonable
stipend and shall reimburse Executive for reasonable expenses incurred as a
result of Executive's cooperation with the Company. This provision shall survive
any termination of this Agreement.

               l. Withholding Taxes. The Company may withhold from any amounts
payable under this Agreement such Federal, state and local taxes as may be
required to be withheld pursuant to any applicable law or regulation.

               m. Counterparts. This Agreement may be signed in counterparts,
each of which shall be an original, with the same effect as if the signatures
thereto and hereto were upon the same instrument.

               n. Shareholder Approval. This Agreement shall be subject to, and
shall only be effective following, the approval of the Company's shareholders as
of the date hereof who owned, as of the date hereof, more than 75% of the voting
power of all outstanding stock of the Company, determined and obtained in a
manner consistent with the methodology described in proposed Treasury Regulation
Section 1.280G-1, or any successor thereto.

<PAGE>

                                                                              13

         IN WITNESS WHEREOF, the parties hereto have duly executed this

Agreement as of the day and year first above written.

         PREMCOR INC.


         /s/ Thomas D. O'Malley                         /s/ Henry Kuchta
--------------------------------------------         ---------------------------
By:      THOMAS D. O'MALLEY                             HENRY KUCHTA
Title:   Chairman, President,
         Chief Executive Officer and
         Chief Operating Officer