<PAGE>

                                                                   EXHIBIT 10.25

                              EMPLOYMENT AGREEMENT


     EMPLOYMENT AGREEMENT (the "Agreement") dated March 1, 2000 by and between
Clark Refining & Marketing, Inc. (the "Company") and Jeffry N. Quinn (the
"Executive").

     WHEREAS, the Company considers it essential to its best interests and the
best interests of its stockholders to foster the employment of Executive by the
Company during the term of this Agreement and Executive is willing to accept
Executive's employment on the terms hereinafter set forth in this Agreement;

     NOW, THEREFORE, in consideration of the premises and mutual covenants
herein and for other good and valuable consideration, the parties agree as
follows:

1.   Term of Employment; Executive Representation.
     --------------------------------------------

     a. Employment Term.  Subject to the provisions of Section 8 of this
        ---------------
     Agreement, Executive shall be employed by the Company for the three-year
     period commencing on March 1, 2000 and ending on February 28, 2003 (the
     "Employment Term") on the terms and subject to the conditions set forth in
     this Agreement.  Notwithstanding the preceding sentence, commencing March
     1, 2003, and on each anniversary thereof thereafter (each anniversary, an
     "Extension Date"), the Employment Term shall be automatically extended for
     an additional one-year period, unless either party provides the other party
     hereto with 60 days' written notice prior to the next Extension Date that
     the Employment Term shall not be so extended.  For the avoidance of doubt,
     the term "Employment Term" shall include any extension that becomes
     applicable pursuant to the preceding sentence.

     b. 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 the 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.

2.   Position.
     --------

     a.  While employed hereunder, Executive shall serve as the Company's
     Executive Vice-President-Legal, Human Resources, and Public Affairs and as
     an Executive Vice-President of Clark Refining Holdings, Inc. and Clark USA,
     Inc.  Executive shall also serve as the Company's General Counsel, or such
     other title as shall denote his status as the chief legal officer of the
     Company.  However, nothing contained herein shall in any way restrict the
     ability of the Company to assign Executive, with his consent, to other
     positions of equivalent status within the Company. In such positions,
     Executive shall have such duties and authority as shall be determined from
     time to time by the Board of Directors of the Company (the "Board"), and
     the Executive shall report directly to the Chief Executive Officer of the
     Company.  If requested, the Executive shall also serve as a member of the
     Board or the boards of any affiliates of the Company without additional
     compensation.
<PAGE>

                                                                               2



     b.  While employed hereunder, Executive will devote Executive's full
     business time and best efforts to the performance of Executive's duties
     hereunder and will not engage in any other business, profession or
     occupation for compensation or otherwise which would conflict with the
     rendition of such services either directly or indirectly; provided that
                                                               --------
     nothing herein shall preclude Executive, subject to the prior approval of
     the Chief Executive Officer, from accepting appointment to the 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 interfere with the performance of Executive's duties
     hereunder or conflict with Section 9.  Any compensation earned by Executive
     for serving in such director or trustee capacity shall be the sole and
     exclusive property of Executive.

3.   Base Salary.   While employed hereunder, the Company shall pay Executive a
     -----------
base salary (the "Base Salary") at the annual rate of $282,500, 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,
and any such increased Base Salary shall be deemed to be Executive's "Base
Salary" for purposes of this Agreement.

4.   Bonuses.
     -------

     a.   Signing Bonus.  As consideration for Executive's entering into this
          -------------
     Agreement, the Company shall pay Executive a one-time signing bonus of
     $125,000, payable as soon as practicable after the date hereof.

     b.   Annual Bonus.  With respect to each calendar year while employed
          ------------
     hereunder, Executive shall be eligible to earn an annual bonus award
     pursuant to the Company's annual incentive plan (the "Annual Incentive
     Plan") in an amount to be determined at the sole discretion of the Board in
     consultation with the Chief Executive Officer. Executive's Annual Bonus
     Opportunity (as defined in the Annual Incentive Plan) shall be 150% of Base
     Salary and his Annual Target Bonus (as defined in the Annual Incentive
     Plan) shall be 100% of Base Salary. However, Executive's Annual Bonus
     Opportunity and Annual Target Bonus shall be subject to change based upon
     modifications made from time to time to the Annual Incentive Plan by the
     Company's management team, which team shall include the Executive,
     provided, however, that in any such modification of the Annual Incentive
     Plan Executive's Annual Bonus Opportunity and Annual Target Bonus shall be
     no less than that of other similarly situated officers of the Company,
     including any Executive Vice President thereof.  Notwithstanding the
     foregoing, Executive shall be entitled to an annual bonus of at least
     $100,000 in respect of calendar year 2000.

5.   Equity Arrangements.  Executive shall be granted an option to purchase
     -------------------
120,000 shares of the common stock of Clark Refining Holdings Inc. (the "Common
Stock") pursuant to the terms of the Clark Refining Holdings Inc. 1999 Stock
Incentive Plan (the "Stock Incentive Plan").  The option shall have a per share
exercise price of $9.90.

     The options for 60,000 shares shall vest ratably over the four years
following the date hereof (1/4 per year), and the options for the remaining
60,000 shares shall vest on the seventh
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                                                                               3

anniversary of the grant date, or upon the achievement of the share prices set
forth below for the Common Stock: (i) following an initial public offering, as
an average closing price for any 180 day consecutive period, or (ii) in a Change
in Control:

     Per Share Price                            % Vested
   ------------------                         ------------
     below    $12.00                                 0%
     $12.00 - $14.99                                10%
     $15.00 - $17.99                                20%
     $18.00 - $19.99                                30%
     $20.00 - $24.99                                50%
     $25.00 - $29.99                                75%
     above    $29.99                               100%

     The specific terms of such grant shall be set forth in a separate option
agreement, and shall be subject to the terms of the Stock Incentive Plan.


6.   Employee Benefits.
     -----------------

     a.   Welfare and Pension Benefits.  The Company shall provide Executive
          ----------------------------
     during the term of his employment hereunder with coverage under all
     employee pension and welfare benefit programs, plans and practices in
     accordance with the terms thereof, which the Company generally makes
     available to its senior executives; provided, however, that the Company
                                         --------  -------
     shall reimburse Executive for the cost of COBRA continuation coverage
     (elected by Executive under his prior employer's group health plan) during
     the first 30 days of the Employment Term (after which time Executive will
     be eligible for coverage under the Company's medical plan pursuant to this
     Section 6(a)).

     b.   Vacation and Other Perquisites.  Executive shall also be entitled to
          ------------------------------
     such number of paid vacation and sick leave days in each calendar year as
     established under the Company's policies as in effect from time to time,
     which shall be taken at such times as are consistent with Executive's
     responsibilities hereunder. In addition, the Company shall reimburse
     Executive for the reasonable cost of financial, estate and tax preparation
     and planning services listed on Exhibit A incurred by Executive during the
     calendar year 2000, upon presentation by Executive from time to time of
     appropriately itemized accounts of such expenditures.  Such accounts shall
     be subject to approval by the Chief Executive Officer.

7.   Business Expenses.   Executive is authorized to incur reasonable expenses
     -----------------
in carrying out his duties and responsibilities under this Agreement, including,
without limitation, expenses for travel and similar items related to such duties
and responsibilities.  The Company will reimburse Executive for all such
expenses upon presentation by Executive from time to time of appropriately
itemized and approved (consistent with the Company's policy) accounts of such
expenditures.
<PAGE>

                                                                               4

8.   Termination.  The Executive's employment hereunder may be terminated by
     -----------
either party at any time and for any reason; provided that Executive will be
                                             --------
required to give the Company at least 60 days advance written notice of any
resignation of Executive's employment.  Notwithstanding any other provision of
this Agreement, the provisions of this Section 8 shall exclusively govern
Executive's rights upon termination of employment with the Company and its
affiliates.  Upon termination of Executive's employment for any reason,
Executive agrees to resign, as of the date of such termination, from the Board
and the board of directors of any of the Company's affiliates.

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

          (i) Executive's employment hereunder may be terminated by the Company
          for Cause (as defined below) at any time or, upon 60 days prior
          written notice, by Executive without Good Reason (as defined below).

          (ii) For purposes of this Agreement, "Cause" shall  mean (A)
          Executive's continued failure to substantially 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 10 days
          following written notice by the Company to Executive of such failure,
          (B) dishonesty in the performance of Executive's duties hereunder, (C)
          an act or acts on Executive's part constituting (x) a felony under the
          laws of Missouri or (y) a misdemeanor involving moral turpitude, (D)
          Executive's willful malfeasance or willful misconduct in connection
          with Executive's duties hereunder or any act or omission which is
          materially injurious to the financial condition or business reputation
          of the Company or any of its subsidiaries or affiliates, (E)
          Executive's breach of the restrictive covenants set forth in Section 9
          hereof or (F) Executive's failure to substantially perform Executive's
          duties hereunder (other than as a result of total or partial
          incapacity due to physical or mental illness) at the Company's
          location in the St. Louis, Missouri metropolitan area, except as
          otherwise required by the Company.

          (iii)  If Executive's employment is terminated by the Company for
          Cause or by Executive 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 calendar year;

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

               (D) such employee benefits, if any, as to which Executive may be
               entitled under the employee benefit plans of the Company (the
               amounts

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                                                                               5


               described in clauses (A) through (D) hereof being referred to as
               the "Accrued Rights").

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

     b.   Disability or Death.
          -------------------

          (i) Executive's employment hereunder shall terminate upon Executive's
          death or if Executive becomes physically or mentally incapacitated, as
          determined pursuant to the Company's long-term disability program as
          may be in effect from time to time (the "LTD Program"), and is
          therefore unable, for a period of time as determined under the LTD
          Program, 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; and

               (B) a pro rata portion of Executive's annual target bonus based
               upon the percentage of the calendar year that shall have elapsed
               through the date of termination of the Executive's employment,
               payable when such bonus would have otherwise been payable had
               Executive's employment not terminated.

          Following Executive's termination of employment due to death or
     Disability, except as set forth in this Section 8(b), Executive shall have
     no further rights to any compensation or any other benefits under this
     Agreement.
<PAGE>

                                                                               6


     c.   By the Company Without Cause, Expiration of Employment Term, or
          ---------------------------------------------------------------
Resignation by Executive for Good Reason.
----------------------------------------

          (i) The Executive's employment hereunder may be terminated by the
          Company without Cause, by the Company's election not to extend the
          Employment Term, or, upon 60 days prior written notice, by Executive's
          resignation for Good Reason.

          (ii) In the event that the Company 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.

          (iii)  For purposes of this Agreement, "Good Reason" shall mean: (A) a
          reduction in Executive's Base Salary or annual bonus opportunity or
          target bonus (other than any general salary reduction affecting at
          least the majority of salaried employees or annual incentive plan
          changes affecting all similarly situated officers of the Company,
          including any Executive Vice President, and provided that the
          establishment of reasonable performance targets by the Board will not
          constitute a reduction of annual bonus opportunity or target bonus),
          (B) a substantial diminution of Executive's duties and
          responsibilities, or (C) a transfer of Executive's primary workplace
          by more than thirty-five (35) miles from the Executive's workplace
          immediately prior to such transfer.

               Notwithstanding the foregoing, none of the events described in
          clauses  (A), (B) or (C) of this Section 8(c)(ii) shall constitute
          Good Reason unless Executive shall have notified the Company in
                      ------
          writing describing the events which constitute Good Reason and then
          only if the Company shall have failed to cure such event within thirty
          (30) days after the Company's receipt of such written notice.
          However, any termination of Executive's employment by the Company
          after delivery by the Executive to the Company of such notice shall be
          deemed to be a termination without Cause if Good Reason did exist at
          the time such notice was given by Executive.

          (iv) If Executive's employment is terminated by the Company without
          Cause (other than by reason of death or Disability), as a result of
          the Company's nonrenewal of the Employment Term pursuant to Section 1
          hereof, or by Executive's resignation for Good Reason, Executive shall
          be entitled to receive:

               (A)  the Accrued Rights; and

               (B) subject to Executive's continued compliance with the
               provisions of Section 9, an amount equal to two (the "Severance
               Multiplier") times the sum of the (1) then Base Salary and (2)
               then annual target bonus, payable
<PAGE>

                                                                               7


               in accordance with normal payroll practices of the Company in
               substantially equal installments over the 24 month period
               following termination of employment; provided that the aggregate
                                                    --------
               amount described in this clause (B) shall be reduced by the
               present value of any other cash severance or termination benefits
               payable to Executive under any other plans, programs or
               arrangements of the Company or its affiliates.

                    Notwithstanding the foregoing, in the event Executive's
               employment is terminated under this Section 8(c) at any time
               following a Change of Control (defined below), the Severance
               Multiplier shall be increased from two to three, and any
               severance amounts payable pursuant to Section 8(c)(iv)(B) shall
               be payable in the form of a single, lump sum cash payment within
               10 days following termination of employment.


               (C) The Company, at its expense, shall provide the Executive with
               the reasonable job relocation counseling services of a firm
               chosen from time to time by the Executive, for a period not to
               exceed 18 months after the Date of Termination.

               (D) The Company shall maintain in full force and effect, for the
               Executive's continued benefit, until the earlier of (1) one year
               after the date of the termination of Executive's employment or
               (2) the Executive's commencement of full time employment with a
               new employer, all life insurance, medical, dental, health and
               accident and disability plans, programs or arrangements in which
               the Executive was entitled to participate immediately prior to
               the termination of Executive's employment at a cost to the
               Executive no greater than the Executive paid while employed by
               the Company, provided that the Executive's continued
               participation is possible under the general terms and provisions
               of such plans and programs.  In the event that the Executive's
               participation is barred, the Company shall arrange to provide the
               Executive, at the Company's expense, with benefits substantially
               similar to those which the Executive is entitled to receive under
               such plans, programs or arrangements, or pay cash in an amount
               after tax sufficient to enable the Executive to purchase
               substantially similar coverage for a one year period on an
               individual basis, at a cost to the Executive no greater than the
               Executive paid while employed.  In the case of the Executive's
               commencement of full time employment with a new employer within
               the one year period, the Company agrees to make up any
               differential in benefits between what the Executive would have
               received from the Company in the one year period and what the
               Executive receives from his new employer, so that the Executive
               is ensured of receiving the same benefits which he would have
               been entitled to receive from the Company had his employment with
               the Company continued for the one year period
<PAGE>

                                                                               8

               at a cost to the Executive no greater than the Executive paid
               while employed.

          Following Executive's termination of employment by the Company without
     Cause (other than by reason of Executive's death or Disability), as a
     result of the Company's nonrenewal of the Employment Term pursuant to
     Section 1 hereof, or by Executive's resignation for Good Reason, except as
     set forth in this Section 8(c), Executive shall have no further rights to
     any compensation or any other benefits under this Agreement.

     d. 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 11(h) 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.

     e.  Definition of Change of Control.  For purposes hereof, "Change of
         -------------------------------
     Control" shall mean any transaction, the result of which is that any Person
     (an "Acquiring Person") other than (i) Blackstone (defined below) or (ii)
     any Person, a majority of whose voting equity is owned by Blackstone,
     becomes the beneficial owner, directly or indirectly, of shares of stock of
     the Company or Clark US, Inc. entitling such Acquiring Person to exercise
     50% or more of the total voting power of all classes of stock of the
     Company or Clark USA, Inc., as the case may be, entitled to vote in
     elections of directors.  For purposes hereof, "Blackstone" shall mean,
     collectively, The Blackstone Group, Blackstone Capital Partners III
     Merchant Banking Fund L.P., and their affiliates (other than the Company
     and its subsidiaries) and "Person" shall mean a "person" as such term is
     used for purposes of Section 13(d) or 14(d) of the Securities Exchange Act
     of 1934, as amended.

     f.  (i) In the event it shall be determined that any payment, benefit or
         distribution (or combination thereof) by the Company, or by any other
         member of the same affiliated group with the Company (as determined
         under Code Section 280G(d)(5)) for the benefit of the Executive
         (whether paid or payable or distributed or distributable pursuant to
         the terms of this Agreement, or otherwise) (a "Payment") would be
         subject to the excise tax imposed by Section 4999 of the Internal
         Revenue Code of 1986, as amended from time to time (the "Code"), or any
         interest or penalties are incurred by the Executive with respect to
         such excise tax (other than interest or penalties incurred as a result
         of the failure of the Executive to file any tax return, or pay any tax
         (except any such failure to pay tax in accordance with the terms
         hereof), required by applicable law or to be filed or paid by the
         Executive) (such tax together with any such interest and penalties,
         hereinafter collectively referred to as the "Excise Tax"), the
         Executive shall be entitled to receive an additional payment (a "Gross-
         Up Payment") in an amount such that after payment by the Executive of
         taxes (including payroll taxes and any interest or penalties imposed
         with respect to such taxes, other than interest or penalties imposed as
         a result of the failure of the Executive to file any tax return
<PAGE>

                                                                               9



          or pay any tax (except any such failure to pay tax in accordance with
          the terms hereof), required by applicable law to be filed or paid by
          the Executive), including, without limitation, any income taxes (and
          any interest and penalties imposed with respect thereto, other than
          interest or penalties imposed as a result of the failure of the
          Executive to file any tax return or pay any tax (except any such
          failure to pay tax in accordance with the terms hereof), required by
          applicable law to be filed or paid by the Executive) and the Excise
          Tax imposed upon the Gross-Up Payment, the Executive retains an amount
          of the Gross-Up Payment equal to the Excise Tax imposed upon the
          Payments.

          (ii) Subject to the provisions of subsection 8(g)(iii), all
          determinations required to be made under this subsection 8(g),
          including whether and when a Gross-Up Payment is required and the
          amount of such Gross-Up Payment and the assumptions to be utilized in
          arriving at such determination, shall be made by Deloitte & Touche LLP
          or, if Deloitte & Touche LLP is unable or unwilling to serve, then
          such nationally recognized accounting firm as the Company shall select
          (Deloitte & Touche LLP or such other accounting firm being the
          "Accounting Firm" ), which shall provide detailed supporting
          calculations both to the Company and the Executive within fifteen (15)
          business days of the receipt of notice from the Executive that there
          has been a Payment, or such earlier time as is requested by the
          Company. All fees and expenses of the Accounting Firm shall be borne
          solely by the Company. Any Gross-Up Payment, as determined pursuant to
          this Section 8(g), shall be paid by the Company to the Executive
          within five (5) days after the receipt of the Accounting Firm's
          determination. If the Accounting Firm determines that no Excise Tax is
          payable by the Executive, it shall so indicate to the Executive in
          writing. Any determination by the Accounting Firm shall be binding
          upon the Company and the Executive. As a result of the uncertainty in
          the application of Section 4999 of the Code at the time of the initial
          determination by the Accounting Firm hereunder, it is possible that
          Gross-Up Payments which will not have been made by the Company should
          have been made ("Underpayment"), consistent with the calculations
          required to be made hereunder. In the event that the Corporation
          exhausts its remedies pursuant to subsection 8(g)(iii) and the
          Executive thereafter is required to make a payment of any Excise Tax,
          the Accounting Firm shall determine the amount of the Underpayment
          that has occurred and any such Underpayment shall be promptly paid by
          the Corporation to or for the benefit of the Executive.

          (iii)  The Executive shall notify the Company in writing of any claim
          by the Internal Revenue Service 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 ten (10)
          business days after the Executive is informed in writing of such claim
          and shall apprize the Company of the nature of such claim and the date
          on which such claim is requested to be paid. The Executive shall not
          pay such claim prior to the expiration of the thirty (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
          respect to such claim is
<PAGE>

                                                                              10

          due). If the Company notifies the Executive in writing prior to the
          expiration of such period that it desires to contest such claim, the
          Executive shall:

               (A) give the Company any information requested by the Company
               relating to such claim;

               (B) 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;

               (C) cooperate with the Company in good faith in order to
               effectively contest such claim; and

               (D) permit the Company to participate in any proceedings relating
               to such claim; provided, however, that the Company shall bear and
               pay directly all 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, for any Excise Tax or income tax (including interest
               and penalties with respect thereto, other than interest or
               penalties imposed as a result of the failure of the Executive to
               file any tax return or pay any tax (except any such failure to
               pay tax in accordance with the terms hereof), required by
               applicable law to be filed or paid by the Executive) imposed as a
               result of such representation and payment of costs and expenses,
               Without limitation on the foregoing provisions of this subsection
               8(g)(iii), the Company shall control all proceedings taken in
               connection with such content 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 the
               Executive to pay the tax claimed and sue for a refund or contest
               the claim in any permissible manner, and the 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;
               provided, however, that of 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, other than interest
               or penalties imposed as a result of the failure of the Executive
               to file any tax return or pay any tax (except any such failure to
               pay tax in accordance with the terms hereof), required by
               applicable law to be filed or paid by the Executive) imposed with
               respect to such advance or with respect to any imputed income
               with respect to such advance; and provided, further, that if the
               Executive is required to extend the statute of limitations to
               enable the Company to contest such
<PAGE>

                                                                              11

               claim, the Executive may limit this extension solely to such
               contested amount. 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.

          (iv) If, after the receipt by the Executive of an amount advanced by
          the Company pursuant to subsection 8(g)(iii), the Executive becomes
          entitled to receive any refund with respect to such claim, the
          Executive shall (subject to the Company's complying with the
          requirements of subsection 8(g)(iii)) 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 receipt by the
          Executive of an amount advanced by the Company pursuant to subsection
          8(g)(iii), 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 thirty (30) days after
          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.

9.   Nondisclosure of Confidential Information; Non-Solicitation.
     -----------------------------------------------------------

     a. At any time during or for a period of three years after Executive's
     employment with the Company, Executive shall not, without the prior written
     consent of the Company, use, divulge, disclose or make accessible to any
     other person, firm, partnership, corporation or other entity any
     Confidential Information (as hereinafter defined) pertaining to the
     business of the Company or any of its subsidiaries, except (i) while
     employed by the Company, in the business of and for the benefit of the
     Company, or (ii) when required to do so by a court of competent
     jurisdiction, by any governmental agency having supervisory authority over
     the business of the Company, or by any administrative body or legislative
     body (including a committee thereof) with jurisdiction to order Executive
     to divulge, disclose or make accessible such information.  For purposes of
     this Section 8(a), "Confidential Information" shall mean non-public
     information concerning the financial data, strategic business plans, and
     other non-public, proprietary and confidential information of the Company,
     its subsidiaries, Blackstone (defined above), and their respective
     affiliates as in existence as of the date of Executive's termination of
     employment that, in any case, is not otherwise available to the public
     (other than by Executive's breach of the terms hereof).

     b. In the course of Executive's employment Executive will acquire knowledge
     of Confidential Information and trade secrets.  Executive acknowledges that
     the Confidential Information and trade secrets which the Company has
     provided and will provide to him could play a significant role were he to
     directly or indirectly be engaged in any business that competes with the
     Company or its subsidiaries.  Executive agrees that, without the prior
     written consent of the Company, (i) during his employment with the Company
     and
<PAGE>

                                                                              12

     for a period of two years thereafter he shall not, on his own behalf or
     on behalf of any person, firm or company, directly or indirectly, solicit
     the business of any person or entity that has been a client or customer of
     the Company or its subsidiaries at any time during the 12 months
     immediately preceding such solicitation, and (ii) during his employment
     with the Company or for a period of one year thereafter he shall not, on
     his own behalf or on behalf of any person, firm or company, directly or
     indirectly, solicit or offer employment to any person who has been employed
     by the Company, its subsidiaries, or Blackstone in an executive or
     management capacity at any time during the 12 months immediately preceding
     such solicitation.

     c. Executive and the Company agree that the foregoing covenants not to
     solicit are a reasonable covenant under the circumstances, and further
     agree that if in the opinion of any court of competent jurisdiction such
     restraints are not reasonable in any respect, such court shall have the
     right, power and authority to excise or modify such provision or provisions
     of these covenants as, to the court, shall appear not reasonable and to
     enforce the remainder of the covenant as so amended.

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

11.  Miscellaneous.
     -------------

     a.  Governing Law.  This Agreement shall be governed by and construed in
         -------------
     accordance with the laws of the State of Missouri, without regard to
     conflicts of laws principles thereof.

     b.  Entire Agreement/Amendments.  This Agreement contains the entire
         ---------------------------
     understanding of the parties with respect to the employment of Executive by
     the Company.  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.  This Agreement supercedes all prior
     agreements and understandings (including verbal agreements) between
     Executive and the Company and/or its affiliates regarding the terms and
     conditions of Executive's employment with the Company and/or its affiliates

     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.
<PAGE>

                                                                              13

     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 to a company which is a successor
     in interest to substantially all of the business operations of the Company.
     Such assignment shall become effective when the Company notifies Executive
     of such assignment or at such later date as may be specified in such
     notice.  Upon such assignment, the rights and obligations of the Company
     hereunder shall become the rights and obligations of such successor
     company, provided that any assignee expressly assumes the obligations,
              --------
     rights and privileges of this Agreement.

     Mitigation.  If the Executive's employment hereunder is terminated for any
     ----------
     reason, the Executive shall not be subject to any duty or obligation to
     seek alternate employment or other sources of income or benefits, or to
     mitigate his damages, or to any similar duty or obligation, and, except as
     specifically provided with respect to the continuation of benefits, all
     payment and other obligations of the Company under this Agreement shall not
     be subject to any rights of set-off, duty to mitigate or other reduction,
     and shall be paid and performed in full notwithstanding any alternate
     employment or other sources of income or benefits obtained or received or
     receivable by the Executive.

     g.  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.

     h.  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 or 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.

     If to the Company:
     Clark Refining & Marketing, Inc.
     c/o Clark USA, Inc.
     8182 Maryland Avenue
     Clayton, Missouri 63105
     Attention:  Corporate Secretary
     If to Executive:
     To the most recent address of Executive set forth in the personnel records
     of the Company.
<PAGE>

                                                                              14


     i.  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.

     j.  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.

     k.  Legal and Professional Fees. The Corporation shall pay to the Executive
         ---------------------------
     all reasonable legal and professional fees and expenses incurred by the
     Executive in seeking to obtain or enforce any right or benefit provided by
     this Agreement.



          IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the day and year first above written.

                              CLARK REFINING & MARKETING, INC.:


                              By:________________________
                              Name:
                              Title:

                              JEFFRY N. QUINN:

                              ___________________________
                              245 Litchford Court
                              Creve Coeur, Missouri 63141


<PAGE>

                                                                              15


                                   EXHIBIT A
          (Financial, Estate and Tax Preparation and Planning Services)


          .  Financial consulting services from AYCO, Inc.

          .  Estate planning work rendered by Gerald Zaft, Attorney-At-Law.

          .  Tax preparation and planning services for 2000 performed by AYCO,
             Inc.