<PAGE>   1





                                                                  EXHIBIT 10.(f)


                                January 1, 1993


Mr. Robert G. Sachse
2302 S. Delaware Place
Tulsa, Oklahoma 74114

Dear Mr. Sachse:

         MAPCO Inc. (the "Corporation") considers it essential to the best
interests of its stockholders to foster the continuous employment of key
management personnel.  In this connection, the Board of Directors (the "Board")
recognizes that, as is the case with many publicly held corporations, the
possibility of a change in control of the Corporation may exist and that such
possibility, and the uncertainty and questions which it may raise among
management, may result in the departure or distraction of management personnel
to the detriment of the Corporation and its stockholders.

         The Board has determined that appropriate steps should be taken to
reinforce and encourage the continued attention and dedication of members of
the Corporation's management, including you, to their assigned duties without
distraction in the face of potentially-disturbing circumstances arising from
the possibility of a change in control of the Corporation.  In that regard, the
Board has determined that this letter agreement (the "Agreement") will serve
the above-stated objective.

         In order to induce you to remain in the employ of the Corporation, the
Corporation agrees that you shall receive the severance benefits set forth in
this Agreement in the event your employment with the Corporation is terminated
under the circumstances described below subsequent to a "change in control of
the Corporation" (as defined in Section 2).

         1.      Term of Agreement.  This Agreement shall commence on January
1, 1993, and shall continue in effect through December 31, 1992; provided,
however, that commencing on January 1, 1994 and each January 1 thereafter, the
term of this Agreement shall automatically be extended for one additional year
unless, not later than October 1 of the preceding year, the Corporation shall
have given notice that it does not wish to extend this Agreement; and provided,
further, that if a change in control of the Corporation, as defined in Section
2, shall have occurred during the original or extended term of this Agreement,
this Agreement shall automatically continue in effect for a period of
twenty-four (24) months beyond the month in which such change in



                                       1
<PAGE>   2
control occurred.  In no event, however, shall the term of this Agreement
extend beyond the end of the calendar month in which your 65th birthday occurs.

         2.      Change in Control.

         (i)     No benefits shall be payable hereunder unless there shall have
been a change in control of the Corporation, as set forth below.  For purposes
of this Agreement, a "change in control of the Corporation" shall be deemed to
have occurred if:

         (A)     any "person," as such term is used in Sections l3(d) and l4(d)
         of the Securities Exchange Act of 1934, as amended (the "Exchange
         Act") (other than the Corporation, any trustee or other fiduciary
         holding securities under an employee benefit plan of the Corporation,
         or any corporation owned, directly or indirectly, by the stockholders
         of the Corporation in substantially the same proportions as their
         ownership of stock of the Corporation), is or becomes the "beneficial
         owner" (as defined in Rule 13d-3 under the Exchange Act), directly or
         indirectly, of securities of the Corporation representing 25% or more
         of the combined voting power of the Corporation's then outstanding
         securities eligible to vote; or

         (B)     during any period of two consecutive years (not including any
         period prior to the execution of this Agreement), individuals who at
         the beginning of such period constitute the Board, and any new
         director (other than a director designated by a person who has entered
         into an agreement with the Corporation to effect a transaction
         described in clause (A), (B) or (D) of this Section) whose election by
         the Board or nomination for election by the Corporation's stockholders
         was approved by a vote of at least two-thirds (2/3) of the directors
         then still in office who either were directors at the beginning of the
         period or whose election or nomination for election was previously so
         approved (hereinafter referred to as "Continuing Directors"), cease
         for any reason to constitute at least a majority thereof;

         (C)     the stockholders of the Corporation approve a merger or
         consolidation of the Corporation with any other corporation, other
         than a merger or consolidation which would result in the voting
         securities of the Corporation outstanding immediately prior thereto
         continuing to represent (either by remaining outstanding or by being
         converted into voting securities of the surviving entity) in
         combination with the ownership of any trustee or other fiduciary
         holding securities under an employee benefit plan of the Company,





                                       2
<PAGE>   3
         more than 75% of the combined voting power of the voting securities of
         the Corporation or such surviving entity outstanding immediately after
         such merger or consolidation; provided, however, that a merger or
         consolidation effected to implement a recapitalization of the
         Corporation (or similar transaction) in which no "person" (as
         hereinabove defined) acquires more than 50% of the combined voting
         power of the Corporation's then outstanding securities shall not
         constitute a change in control of the Corporation; or

         (D)     the stockholders of the Corporation approve a plan of complete
         liquidation of the Corporation or an agreement for the sale or
         disposition by the Corporation of all or substantially all of the
         Corporation's assets (or any transaction having a similar effect).

                 (ii)     You agree that, subject to the terms and conditions
         of this Agreement, in the event of a "potential change in control of
         the Corporation" during the term of this Agreement, the Corporation
         may not terminate this Agreement and you will remain in the employ of
         the Corporation until the earliest of (A) a date which is nine (9)
         months from the date of such potential change in control of the
         Corporation or any earlier date approved by the Board, (B) the date of
         a change in control of the Corporation, (C) the date you terminate
         your employment by reason of death, Disability or Retirement, or (D)
         the termination by the Corporation of your employment for any reason.

                 (iii)    For purposes of this Agreement, a "potential change
         in control of the Corporation" shall be deemed to have occurred if the
         conditions set forth in any one of the following paragraphs shall have
         been satisfied:

         (A)     the Corporation enters into an agreement, the consummation of
         which would result in the occurrence of a change in control of the
         Corporation;

         (B)     any person (including the Corporation) publicly announces an
         intention to take or to consider taking actions which, if consummated,
         would constitute a change in control of the Corporation.

         (C)     any person other than a trustee or other fiduciary holding
         securities under an employee benefit plan of the Corporation (or a
         corporation owned, directly or indirectly by the stockholders of the
         Corporation in substantially the same proportions as their ownership
         of stock of the Corporation), who is or becomes the beneficial owner,
         directly or indirectly, of securities of the Corporation representing
         10% or more of the combined voting power of the





                                       3
<PAGE>   4
         Corporation's then outstanding securities, increases such person's
         beneficial ownership of such securities by 5% or more over the
         percentage so owned by such person on the date hereof; or

         (D)     the Board adopts a resolution to the effect that, for purposes
         of this Agreement, a potential change in control of the Corporation
         has occurred.

         3.      Termination Following Change in Control.

                 (i)      General.  If any of the events described in Section 2
         constituting a change in control of the Corporation shall have
         occurred, you shall be entitled to the benefits provided in Section
         4(iii) upon the subsequent termination of your employment during the
         term of this Agreement unless such termination is (a) because of your
         death or Disability, (b) by the Corporation for Cause, or (c) by you
         other than for Good Reason.  In the event your employment with the
         Corporation is terminated for any reason prior to the occurrence of a
         change in control of the Corporation, and subsequently a change in
         control of the Corporation shall have occurred, you shall not be
         entitled to any benefits hereunder.

                 (ii)     Disability.  If, as a result of your incapacity due
         to physical or mental illness, you shall have been absent from the
         full-time performance of your duties with the Corporation for six (6)
         consecutive months, and within thirty (30) days after written notice
         of termination is given, you shall not have returned to the full-time
         performance of your duties, for purposes of this Agreement your
         employment may be terminated for "Disability."

                 (iii)    Cause.  Termination by the Corporation of your
         employment for "Cause" shall mean termination (a) upon the willful and
         continued failure by you to substantially perform your duties with the
         Corporation (other than any such failure resulting from your
         incapacity due to physical or mental illness or any such actual or
         anticipated failure after the issuance of a Notice of Termination (as
         defined in Subsection 3(v)) by you for Good Reason (as defined in
         Subsection 3(iv))), within ten (10) days after a written demand for
         substantial performance is delivered to you by the Board, which demand
         specifically identifies the manner in which the Board believes that
         you have not substantially performed your duties, or (b) the willful
         engaging by you in conduct which is clearly and materially injurious
         to the Corporation, monetarily or otherwise.  For purposes of this
         Subsection, no act, or failure to act, on your part shall be deemed
         "willful" unless done, or omitted to be done, by you in bad faith and





                                       4
<PAGE>   5
         without reasonable belief that your action or omission was in or not
         opposed to the best interest of the Corporation.  Notwithstanding the
         foregoing, you shall not be deemed to have been terminated for Cause
         unless and until there shall have been delivered to you a copy of a
         resolution duly adopted by the affirmative vote of not less than
         three-quarters (3/4) of the entire membership of the Board at a
         meeting of the Board (after reasonable notice to you and an
         opportunity for you, together with your counsel, to be heard before
         the Board), finding that in the good faith opinion of the Board you
         were guilty of conduct set forth above in this Subsection and
         specifying the particulars thereof in detail.

                 (iv)     Good Reason.  You shall be entitled to terminate your
         employment for Good Reason.  For purposes of this Agreement, "Good
         Reason" shall mean, without your express written consent, the
         occurrence after a change in control of the Corporation of any of the
         following circumstances unless, in the case of paragraphs (a), (e),
         (f), (g) or (h), such circumstances are fully corrected prior to the
         Date of Termination (as defined in Section 3(vi)) specified in the
         Notice of Termination (as defined in Section 3(v)) given in respect
         thereof:


          (a)    the assignment to you of any duties inconsistent with the
                 status of the position in the Corporation that you held
                 immediately prior to the change in control of the Corporation
                 or an adverse alteration in the nature or status of your
                 responsibilities or in the quality or amount of office
                 accommodations or assistance provided to you, from those in
                 effect immediately prior to such change in control;

          (b)    a reduction by the Corporation in your annual base salary as in
                 effect on the date immediately prior to the change in control
                 of the Corporation or as the same may be increased from time
                 to time thereafter;

          (c)    the Corporation's moving you to be based more than 50 miles
                 from the Corporation's offices at which you are principally
                 employed immediately prior to the date of the change in
                 control of the Corporation except for required travel on the
                 Corporation's business to an extent substantially consistent
                 with your present business travel obligations;

          (d)    the failure by the Corporation to pay to you any portion of
                 your current compensation or compensation under any deferred
                 compensation





                                       5
<PAGE>   6
                 program of the Corporation within seven (7) days of the date
                 such compensation is due;

          (e)    the failure by the Corporation to continue in effect any
                 compensation or benefit plan or perquisites in which you
                 participate immediately prior to the change in control of the
                 Corporation which is material to your total compensation,
                 including but not limited to the Corporation's 1981 Stock
                 Appreciation Rights and Stock Option Rights Plan, 1986 Stock
                 Option Plan, 1989 Stock Incentive Plan, the Long-Term
                 Investment Plan, Annual Incentive Compensation Plan, 1986
                 Performance Bonus Plan, Supplemental Retirement Agreement or
                 any successor plans (collectively, the "Compensation Plans"),
                 unless an equitable arrangement (embodied in an ongoing
                 substitute or alternative plan) has been made with respect to
                 such plan, or the failure by the Corporation to continue your
                 participation therein (or in such substitute or alternative
                 plan) on a basis not materially less favorable, both in terms
                 of the amount of benefits provided and the level of your
                 participation relative to other participants, than existed at
                 the time of the change in control of the Corporation;

          (f)    the failure by the Corporation to continue to provide you with
                 benefits substantially similar to those enjoyed by you under
                 any of the Corporation's life insurance, medical, dental,
                 vision, accident or disability plans in which you were
                 participating at the time of the change in control of the
                 Corporation, the taking of any action by the Corporation which
                 would directly or indirectly materially reduce any of such
                 benefits, or the failure by the Corporation to provide you
                 with the number of paid vacation days to which you are
                 entitled on the basis of your years of service with the
                 Corporation in accordance with the Corporation's normal
                 vacation policy in effect at the time of the change in control
                 of the Corporation;

          (g)    the failure of the Corporation to obtain a satisfactory
                 agreement from any successor to assume and agree to perform
                 this Agreement, as contemplated in Section 5 hereof; or

          (h)    any purported termination of your employment that is not
                 effected pursuant to a Notice of Termination satisfying the
                 requirements of Subsection (v) hereof (and, if applicable, the
                 requirements of Subsection





                                       6
<PAGE>   7
                 (iii) hereof), which purported termination shall not be
                 effective for purposes of this Agreement.

         Your right to terminate your employment pursuant to this Subsection
         shall not be affected by your incapacity due to physical or mental
         illness.  Your continued employment shall not constitute consent to,
         or a waiver of rights with respect to, any circumstance constituting
         Good Reason hereunder.

                 (v)      Notice of Termination.  Any purported termination of
         your employment by the Corporation or by you shall be communicated by
         written Notice of Termination to the other party hereto in accordance
         with Section 6.  "Notice of Termination" shall mean a notice that
         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 your
         employment under the provision so indicated.

                 (vi)     Date of Termination.  "Date of Termination" shall
         mean (a) if your employment is terminated for Disability, thirty (30)
         days after Notice of Termination is given (provided that you shall not
         have returned to the full-time performance of your duties during such
         thirty (30)-day period), and (b) if your employment is terminated
         pursuant to Subsection (iii) or (iv) hereof or for any other reason
         (other than Disability), the date specified in the Notice of
         Termination (which, in the case of a termination for Good Reason shall
         not be less than fifteen (15) nor more than sixty (60) days from the
         date such Notice of Termination is given, and in the case of a
         termination for any other reason shall not be less than thirty (30)
         days from the date such Notice of Termination is given); provided,
         however, that if within fifteen (15) days after any Notice of
         Termination is given, or, if later, prior to the Date of Termination
         (as determined without regard to this provision), the party receiving
         such Notice of Termination notifies the other party that a dispute
         exists concerning the termination, then the Date of Termination shall
         be the date on which the dispute is finally determined, either by
         mutual written agreement of the parties, by a binding arbitration
         award, or by a final judgment, order or decree of a court of competent
         jurisdiction (which is not appealable or with respect to which the
         time for appeal therefrom has expired and no appeal has been
         perfected); and provided, further, that the Date of Termination shall
         be extended by a notice of dispute only if such notice is given in
         good faith and the party giving such notice pursues the resolution of
         such dispute with reasonable diligence.  Notwithstanding the pendency
         of any such dispute, the Corporation will continue to pay you your
         full compensation in effect when the notice giving rise





                                       7
<PAGE>   8
         to the dispute was given and continue you as a participant in all
         Compensation Plans, life insurance, medical, dental, vision, accident
         or disability plans and any similar plans in which you were
         participating when the notice giving rise to the dispute was given,
         until the dispute is finally resolved in accordance with this
         Subsection.  Amounts paid under this Subsection are in addition to all
         other amounts due under this Agreement, and shall not be offset
         against or reduce any other amounts due under this Agreement and shall
         not be reduced by any compensation earned by you as the result of
         employment by another employer.

         4.      Compensation During Disability or Upon Termination. Following
a change ln control of the Corporation, you shall be entitled to the following
during a period of disability, or upon termination of your employment, as the
case may be, provided that such period or termination occurs during the term of
this Agreement:

                 (i)      During any period that you fail to perform your
         full-time duties with the Corporation as a result of incapacity due to
         physical or mental illness, you shall continue to receive your base
         salary at the rate in effect at the commencement of any such period,
         together with all compensation payable to you under the Corporation's
         disability plan or program or other similar plan during such period,
         until this Agreement is terminated pursuant to Section 3(ii) hereof.
         Thereafter, or in the event your employment shall be terminated by
         reason of your death, your benefits shall be determined under the
         Corporation's retirement, insurance and other compensation programs
         then in effect in accordance with the terms of such programs.

                 (ii)     If your employment shall be terminated by the
         Corporation for Cause or by you other than for Good Reason, the
         Corporation shall pay you your full base salary through the Date of
         Termination at the rate in effect at the time Notice of Termination is
         given, plus all other amounts or benefits to which you are entitled
         under any Compensation Plan of the Corporation then in effect, and the
         Corporation shall have no further obligations to you under this
         Agreement.

                 (iii)    If your employment by the Corporation shall be
         terminated by you for Good Reason or by the Corporation other than for
         Cause or Disability, then you shall be entitled to the following:

          (a)    the Corporation shall pay to you your full base salary through
                 the Date of Termination at the rate in effect at the time
                 Notice of Termination is given, no later than the fifth day
                 following the Date of Termination, plus





                                       8
<PAGE>   9
                 all other amounts to which you are entitled under any
                 compensation plan of the Corporation, at the time such
                 payments are due;

          (b)    in lieu of any further salary payments to you for periods
                 subsequent to the Date of Termination, the Corporation shall
                 pay as severance pay to you, at the time specified in
                 Subsection (iv) of this Section 4, a single sum severance
                 payment equal to the product of two and one-half (2 1/2) times
                 the sum of your (1) annual salary as in effect as of your Date
                 of Termination, (2) an amount equal to the highest award of
                 annual incentive compensation, if any, made or to be made to
                 you in respect of your performance for the then current
                 calendar year or any of the three calendar years preceding
                 your Date of Termination, and (3) the awards paid to you
                 pursuant to Section 7 of the Performance Bonus Plan or any
                 successor thereto as a result of a change in control of the
                 Corporation;

         (c)     your rights under the Compensation Plans shall be governed by
                 the terms of those respective plans;

         (d)     the Corporation shall pay to you all reasonable and
                 appropriate legal fees and expenses incurred by you as a
                 result of such termination (including all such fees and
                 expenses, if any, reasonably incurred in contesting or
                 disputing by arbitration or otherwise, any such termination or
                 in seeking to obtain or enforce any right or benefit provided
                 by this Agreement or in connection with any tax audit or
                 proceeding to the extent attributable to the application of
                 section 4999 of the Internal Revenue Code of 1986, as amended,
                 (the "Code"), to any payment or benefit provided hereunder);
                 and

         (e)     for a thirty (30) month period after your Date of Termination,
                 the Corporation shall arrange to provide you with benefits
                 substantially similar to those which you were receiving or
                 entitled to receive under the Corporation's life, disability,
                 accident and group health insurance plans or any similar plans
                 in which you were participating immediately prior to the Date
                 of Termination at a cost to you which is no greater than that
                 cost to you in effect at the Date of Termination.  Benefits
                 otherwise receivable by you pursuant to this paragraph (e)
                 shall be reduced to the extent comparable benefits are
                 actually received on your behalf during the thirty (30) month
                 period following your termination, and such benefits actually
                 received by you shall be reported to the Corporation.





                                       9
<PAGE>   10
                 (iv)     If any payments under this Agreement or any other
         payments or benefits received or to be received by you in connection
         with a change in control of the Corporation, or your termination of
         employment (whether pursuant to the terms of this Agreement or any
         other plan, arrangement or agreement with the Corporation, or any
         person affiliated with the Corporation, (the "Severance Payments"))
         will be subject to the tax (the "Excise Tax") imposed by section 4999
         of the Code (or any similar tax that may hereafter be imposed), the
         Corporation shall pay at the time specified below, an additional
         amount (the "Gross-Up Payment") such that the net amount retained by
         you, after deduction of any Excise Tax on the Severance Payments and
         any federal, state and local income tax and Excise Tax upon the
         payment provided for by this Subsection 4(iv), shall be equal to the
         Severance Payments.  For purposes of determining the amount of the
         Gross-Up Payment, the Excise Tax shall be assumed to be at a rate
         equal to the lesser of (I) 20% or (ii) the rate in effect at the time
         the amount of the Gross-Up payment is determined.  For purposes of
         determining whether any of the Severance Payments will be subject to
         the Excise Tax and the amount of such Excise Tax, (a) all Severance
         Payments shall be treated as "parachute payments" within the meaning
         of section 280G(2) of the Code, and all "excess parachute payments"
         within the meaning of section 28OG(b)(l) shall be treated as subject
         to the Excise Tax, unless in the opinion of tax counsel selected by
         the Corporation's independent auditors and acceptable to you, such
         Severance Payments (in whole or in part) do not constitute parachute
         payments, or such excess parachute payments (in whole or in part)
         represent reasonable compensation for services actually rendered
         within the meaning of section 280G(b)(4) of the Code in excess of the
         base amount within the meaning of section 280G(b)(3) of the Code, or
         are otherwise not subject to the Excise Tax, (b) the amount of the
         Severance Payments which shall be treated as subject to the Excise Tax
         shall be equal to the lesser of (1) the total amount of the Severance
         Payments or (2) the amount of excess parachute payments within the
         meaning of section 28OG(b)(l) (after applying clause (a), above), and
         (C) the value of  any non-cash benefits or any deferred payment or
         benefit shall be determined by the Corporation's independent auditors
         in accordance with the principles of section 280G(d) (3) and (4) of
         the Code.  For purposes of determining the amount of the Gross-Up
         Payment, you shall be deemed to pay federal income taxes at your
         highest marginal rate of federal income taxation in the calendar year
         in which the Gross-Up Payment is to be made and state and local income
         taxes at your highest marginal rate of taxation in the state and
         locality of your residence on the Date of Termination, net of the
         maximum reduction in federal income taxes which could be obtained from
         deduction of such state and local taxes.  In the event that the Excise
         Tax is subsequently





                                       10
<PAGE>   11
         determined to be less than the amount taken into account hereunder at
         the time of termination of your employment, you shall repay to the
         Corporation at the time that the amount of such reduction in Excise
         Tax is finally determined the portion of the Gross-Up Payment
         attributable to such reduction (plus the portion of the Gross-Up
         Payment attributable to the Excise Tax and federal and state and local
         income tax imposed on the Gross-Up Payment being repaid by you if such
         repayment results in a reduction in Excise Tax and/or a federal and
         state and local income tax deduction) plus interest on the amount of
         such repayment at the rate provided in section 1274(b)(2)(B) of the
         Code (the "Applicable Rate").  In the event that the Excise Tax is
         determined to exceed the amount taken into account hereunder at the
         time of the termination of your employment (including by reason of any
         payment the existence or amount of which cannot be determined at the
         time of the Gross-Up Payment), the Corporation shall make an
         additional gross-up payment in respect of such excess (plus any
         interest payable with respect to such excess at the Applicable Rate)
         at the time that the amount of such excess is finally determined.  Any
         payment to be made to you under this paragraph shall be payable within
         five (5) days of your Date of Termination.

                 (v)      The payments provided for in paragraphs (b) and (c)
         above, shall be made not later than the fifth day following the Date
         of Termination; provided, however, that if the amounts of such
         payments cannot be finally determined on or before such day, the
         Corporation shall pay to you on such day an estimate, as determined in
         good faith by the Corporation, of the minimum amount of such payments
         and shall pay the remainder of such payments (together with interest
         at the Applicable Rate) as soon as the amount thereof can be
         determined but in no event later than the thirtieth day after the Date
         of Termination.  In the event that the amount of the estimated
         payments exceeds the amount subsequently determined to have been due,
         such excess shall constitute a loan by the Corporation to you, payable
         on the fifth day after demand by the Corporation (together with
         interest at the Applicable Rate).

                 (vi)     Except as required in Subsection (iii)(e) hereof, you
         shall not be required to mitigate the amount of any payment provided
         for in this Section 4 by seeking other employment or otherwise, nor
         shall the amount of any payment or benefit provided for in this
         Section 4 be reduced by any compensation earned by you as the result
         of employment by another employer, by retirement benefits, by offset
         against any amount claimed to be owed by you to the Corporation, or
         otherwise.





                                       11
<PAGE>   12
         5.      Successors; Binding Agreement.

                 (i)      The Corporation will require any successor whether
         direct or indirect, by purchase, merger, consolidation or otherwise)
         to all or substantially all of the business and/or assets of the
         Corporation to (A) expressly assume and agree to perform this
         Agreement in the same manner and to the same extent that the
         Corporation would be required to perform it if no such succession had
         taken place and (B) agree to notify you of the assumption of the
         Agreement within 10 days of such assumption.  Failure of the
         Corporation to obtain such assumption and agreement prior to the
         effectiveness of any such succession shall be a breach of this
         Agreement and shall entitle you to compensation from the Corporation
         in the same amount and on the same terms to which you would be
         entitled hereunder if you terminate your employment for Good Reason
         following a change in control of the Corporation, except that for
         purposes of implementing the foregoing, the date on which any such
         succession becomes effective shall be deemed the Date of Termination.
         As used in this Agreement, "Corporation" shall mean the Corporation
         and any successor to its business and/or assets as aforesaid which
         assumes and agrees to perform this Agreement by operation of law, or
         otherwise.

                 (ii)     This Agreement shall inure to the benefit of and be
         enforceable by you and your personal or legal representatives,
         executors, administrators, successors, heirs, distributees, devisees
         and legatees.  If you should die while any amount would still be
         payable to you hereunder had you continued to live, all such amounts,
         unless otherwise provided herein, shall be paid in accordance with the
         terms of this Agreement to your devisee, legatee or other designee or,
         if there is no such designee, to your estate.

         6.      Notice.  For the purpose of this Agreement, notices and all
other communications provided for in this Agreement shall be in writing and
shall be deemed to have been duly given when delivered or mailed by United
States certified or registered mail, return receipt requested, postage prepaid,
addressed to the respective addresses set forth on the first page of this
Agreement, provided that all notice to the Corporation shall be directed to the
attention of the Board with a copy to the Secretary of the Corporation, 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.

         7.      Miscellaneous.  No provision of this Agreement may be
modified, waived or discharged unless such waiver, modification or discharge is
agreed to in





                                       12
<PAGE>   13
writing and signed by you and such officer as may be authorized by the Board.
No waiver by either party hereto at any time of any breach by the other party
hereto of, or compliance with, any condition or provision of this Agreement to
be performed by such other  party shall be deemed a waiver of similar or
dissimilar provisions or conditions at the same or at any prior or subsequent
time.  No agreements or representations, oral or otherwise, express or implied,
with respect to the subject matter hereof have been made by either party which
are not expressly set forth in this Agreement.  The validity, interpretation,
construction and performance of this Agreement shall be governed by the laws of
the State of Delaware without regard to its conflicts of law principles.  All
references to sections of the Code shall be deemed also to refer to any
successor provisions to such sections.  Any payments provided for hereunder
shall be paid net of any applicable withholding required under federal, state
or local law, except for any withholding that may be required under Section
4999 of the Code.  The obligations of the Corporation under Section 4 shall
survive the expiration of the term of this Agreement.  This Agreement may be
executed in several counterparts, each of which shall be deemed to be an
original but all of which together will constitute one and the same instrument.

         8.      Validity.  The invalidity or unenforceability of any provision
of this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement, which shall remain in full force and effect.

         9.      Options. The Executive covenants and agrees that he will
exercise, on or before December 31, 1997, all of his outstanding stock options
of the Corporation which are exercisable as of the date hereof and which become
exercisable on or before December 31, 1997.  Notwithstanding the provisions of
Section 4, no payment will be made to the Executive thereunder until and unless
the Executive satisfies the covenant set forth in the preceding sentence.  The
Executive also hereby acknowledges that his stock options outstanding at the
Effective Time will be cancelled at the Effective Time by converting the excess
of the aggregate spread value related thereto into a number of shares of the
common stock of the Parent, on the terms and conditions set forth in the Merger
Agreement.

         10.     Arbitration.  Any dispute or controversy arising under or in
connection with this Agreement shall be settled exclusively by binding
arbitration, conducted before a panel of three arbitrators in the City of
Tulsa, Oklahoma or, at your option, in the city where you are principally
employed immediately prior to the date of a change in control, in accordance
with the rules of the American Arbitration Association then  in effect;
provided, however, that you shall be entitled to seek specific performance of
your rights under Section 3(vi)  during  the pendency of any dispute or





                                       13
<PAGE>   14
controversy arising under or in connection with this Agreement. Judgment may be
entered on the arbitrator's award in any court having jurisdiction.

         11.     Entire Agreement.  This Agreement is an amendment and
restatement of an agreement adopted as of the date first written above, and as
so amended and restated, shall operate as if in effect from such date. This
Agreement sets forth the entire agreement of the parties hereto in respect of
the subject matter contained herein and supersedes all prior agreements
(including, without limitation, any and all prior versions hereof), promises,
covenants, arrangements, communications, representations or warranties, whether
oral or written, by any officer, employee or representative of any party
hereto.  If this letter sets forth our agreement on the subject matter hereof,
kindly sign and return to the Corporation the enclosed copy of this letter,
which will then constitute our agreement on this subject.

                                   Sincerely,


ATTEST:                            MAPCO Inc.

By /s/ JAMES N. CUNDIFF              By /s/ JAMES E. BARNES
  -------------------------             ---------------------------
  James N. Cundiff                   Name:  James E. Barnes
  Assistant Secretary                Title: Chairman of the Board, President   
                                            and Chief Executive Officer




AGREED: /s/ ROBERT G. SACHSE
       -------------------------
       Robert G. Sachse



                                       14