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                                                                    Exhibit 10.3


                        AMENDMENT TO ULTRAMAR CORPORATION
                     SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN


         Ultramar Diamond Shamrock Corporation, a Delaware corporation, pursuant
to authority granted by its Board of Directors, hereby adopts the following
amendments to the Ultramar Corporation Supplemental Executive Retirement Plan.
Such amendments shall be effective as of May 1, 2000, subject to such further
limitations and restrictions as are set forth below.

1. The first sentence of Section 4.1(c) (defining "Average Annual Compensation")
is amended and restated in its entirety, effective for any person who remains
employed by Ultramar Diamond Shamrock Corporation on the date set forth above,
as follows:

         "AVERAGE ANNUAL COMPENSATION" shall be determined in the same manner as
         under the Pension Plan except as otherwise set forth herein, and
         provided that, Average Annual Compensation shall also include an
         "average bonus" if (i) the Participant's employment with a
         Participating Employer is terminated for any reason other than Cause on
         or after the first day of the month in which he attains age fifty-five
         (55) or (ii) the Participant remains employed with the Company (or any
         subsidiary or affiliate of the Company) upon the occurrence of a Change
         in Control.

2. Clause (i) of Section 4.1(m) (defining "SERP Interest Rate"), is amended and
restated, in its entirety, as follows:

         (i) with respect to the computation of the amount of a lump sum benefit
         upon a Change in Control under Section 4.2(e), the interest rate issued
         by the Pension Benefit Guaranty Corporation for private sector lump sum
         payments, as such rate is in effect on the first day of the calendar
         year that contains the date of the distribution.

3. Section 4.1(q)(defining "Trust") is amended and restated in its entirety, as
follows:

                  (q) "TRUST" shall mean the Ultramar Diamond Shamrock
         Corporation Benefits Trust between the Company and Sterling National
         Bank and Trust Company of New York, as it may be amended from time to
         time.

4. The first sentence of Section 4.2(b) is amended and restated, in its
entirety, as follows:

         A Participant who retires from employment with a Participating Employer
         (other than on account of a termination for Cause) on or after the
         first day of the month following his attainment of age sixty-two (62)
         (with the determination of such Participant's then age calculated by
         taking into account any additional years considered added to such
         Participant's actual age pursuant to the terms of any separate
         agreement between the Participant and the Company pertaining to such
         person's participation in the SERP) and who is entitled to a benefit
         under the Pension Plan shall be entitled to receive the greater of the
         Supplemental Pension determined under Section 4.2(a) or this Section
         4.2(b).


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5. The first sentence of clause (ii) of Section 4.2(e) is amended and restated,
in its entirety, effective for any person who remains employed by Ultramar
Diamond Shamrock Corporation on the date set forth above, as follows:

         If there is a Change in Control, each Participant who remains employed
         by the Company (or any subsidiary or affiliate) on the Change in
         Control Date shall be (i) one hundred percent (100%) vested in his
         Supplemental Pension and (ii) paid a single lump sum payment in cash
         equal to the Actuarial Equivalent lump sum value of his Supplemental
         Pension, determined as of the date of the Change in Control using the
         SERP Interest Rate and SERP Mortality Table, in lieu of all other
         benefits under the SERP; provided that any amendment of the SERP made
         within the six-month period ending on the effective date of the Change
         in Control shall be ignored for purposes of computing the amount of the
         lump sum payment under this clause (ii) to the extent that the
         application of such amendment would cause the amount of the lump sum to
         be less than that computed without application of such amendment.

6. Section 4.4(a) is amended and restated, in its entirety, as follows:

                  (a) Any benefit payable to a Participant or Spouse hereunder
         shall be paid by the Company. Notwithstanding the foregoing, such
         benefits shall instead be paid from the Trust, under such circumstances
         (including a Change in Control) as are specified under the terms of the
         Trust. To the extent that the Trust does not pay the benefits under the
         SERP to which any Participant (or Spouse) is entitled, the Company
         remains responsible to do so. Moreover, all assets of the Trust remain,
         at all times, subject to the claims of the Company's creditors in the
         event of the Company's insolvency, and no Participant (or any Spouse
         thereof) shall, at any time, have a prior claim to any Trust assets.

7. Section 4.5 is amended and restated, in its entirety, effective for any
person who remains employed by Ultramar Diamond Shamrock Corporation on the date
set forth above, as follows:

                  4.5 ADDITIONAL TERMS. A Participant shall, subject only to the
         provisions of Section 15, which shall govern in the event of any
         conflict, receive such additional terms (including, but not limited to,
         years of age and/or service for vesting and/or benefit accrual purposes
         under the SERP) as determined by the Committee, in its sole discretion.

8. A new Section 15 is added, effective for any person who remains employed by
Ultramar Diamond Shamrock Corporation on the date set forth above, as follows:

                  15. Special Change in Control Provisions.

                           (a) The provisions of this Section 15 shall apply
                  with respect to each Participant in the group listed in
                  subsection (b) hereof (each, hereafter, a "Covered
                  Participant") who, except as otherwise provided in this
                  Section 15, remains employed by the Company (or any subsidiary
                  or affiliate of the Corporation) (collectively, "UDS") upon
                  the occurrence of a Change in Control. The provisions of this
                  Section 15 shall apply, notwithstanding any other provision of
                  the SERP to the contrary.




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(b)The Covered Participants, identified by social security number, are as
follows:

         [Jean Gaulin]
         [Christopher Havens]
         [H. Pete Smith]

         (c) For purposes of this Section 15, the term "SERP Side Letter" means,
with respect to any Covered Participant, that separate agreement between such
person and the Company pertaining to such person's participation in the SERP, as
such agreement may be amended from time to time.

         (d) Notwithstanding any provisions of the SERP (or of any particular
Covered Participant's SERP Side Letter) to the contrary, the amount of any lump
sum otherwise payable to such person under the SERP on account of being employed
by UDS upon the occurrence of a Change in Control shall be determined in the
following steps, with the lump sum being the amount determined under the
following clause (ii):

         (ii)  Determine the amount of the annual SERP benefit which would
               otherwise be immediately payable to such person, starting on the
               Change in Control Date, and determined as if such person
               terminated employment on the Change in Control Date, and after
               taking into account the foregoing provisions of the SERP, as well
               as such person's SERP Side Letter (other than any provision
               thereof relating to the conversion of such annual SERP benefit
               into a lump sum amount); provided, however, that in making such
               determination, in the event that such person is under age
               sixty-two (62) on the Change in Control Date, (A) the Pension
               Plan benefit and the Other Pension Benefits otherwise taken into
               account in such determination shall be the amount of such
               respective benefits otherwise payable to such person at age
               sixty-two (62) , but with such benefit amounts determined as if
               such person terminated employment on the Change in Control Date,
               and (B) there shall be no reduction on account of early payment
               of the SERP benefit pursuant to the provisions of Section 4.2(c)
               (or otherwise).

         (ii)  Determine the immediate present value, based upon such Covered
               Participant's actual age on the Change in Control Date, of the
               annual benefit amount, calculated under the foregoing clause (i),
               which would otherwise be paid to such person, starting on the
               Change in Control Date, with such present value being determined
               using the interest rate and mortality table set forth in Section
               4.1(m)(i) and Section 4.1(n)(i), respectively (except to the
               extent that a larger lump sum would result from using the
               interest rate and mortality table set forth in Section 4.1(m)(ii)
               and Section 4.1(n)(ii), respectively, in which event the interest
               rate and mortality table set forth in Section 4.1(m)(ii) and
               Section 4.1(n)(ii), respectively, shall instead apply).)



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         (e) Attached to the SERP, as Exhibit A, is a separate schedule for each
Covered Participant illustrating the manner, in accordance with the forgoing
provisions of this Section 15 and the other provisions of the SERP (and the
terms of such person's SERP Side Letter, as such agreement may be modified
pursuant to the foregoing provisions of this Section 15), in which the lump sum
payment to such person with respect to the SERP would, in the event that such
person remains employed by UDS upon the occurrence of a Change in Control, be
calculated for such person, assuming that (I) the Change in Control Date occurs
on December 31, 2000, (II) such lump sum distribution also occurs on that date
and (III) such person remains employed by UDS on that date. In the event of a
Change in Control occurring on December 31, 2000, the amount of the lump sum
payable to any Covered Participant who remains employed by UDS on such date
shall (assuming such lump sum is also paid on that same date) be the amount set
forth with respect to such person in the relevant attached schedule. In the
event that a Change in Control Date occurs on some other date, the methodology
set out in such schedules shall be dispositive in resolving any issues which may
arise in connection with determining the amount of the lump sum otherwise
payable to any such Covered Participant who so remains employed by UDS upon the
occurrence of such other Change in Control Date.

         (f) If a Covered Participant who receives a lump sum distribution on
account of being employed by UDS on a Change in Control Date continues to be
employed by UDS and thereafter becomes entitled to a subsequent distribution
with respect to the SERP, the amount of such subsequent SERP benefit, expressed
as an annual benefit, which annual benefit is the starting point in determining
the amount of such subsequent distribution, shall be equal to the excess of:

         (i)  the amount of the annual SERP benefit, otherwise payable at that
              time (or, at age sixty-two (62), in the event that such person is
              then under age sixty-two (62), determined under the SERP and after
              taking into account the provisions of such person's SERP Side
              Letter, over

         (ii) the amount of the annual SERP benefit which was taken into account
              under clause (i) of the subsection (d) of this Section 15 as the
              starting point in determining the amount of such prior lump sum
              distribution.

         In all other respects, the amount of any subsequent distribution shall
be determined in accordance with such rules of uniform application as may be
established by the Compensation Committee.

         (g) Notwithstanding any other provision of the SERP (or of the Covered
Participant's SERP Side Letter) to the contrary, in the event of such person's
"involuntary termination, other than for Cause" (as those terms are defined
under such person's employment agreement with the Company), in anticipation of a
Change in Control:



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         (i)  the foregoing provisions of this Section 15, and all other
              provisions of the SERP (and of such person's SERP Side Letter)
              shall apply to such person to the same extent as if a Change in
              Control had, solely with respect to such person, occurred on the
              date immediately preceding the date on which such person is so
              terminated from employment, and

         (ii) such Participant's benefit under the Pension Plan, for purposes of
              determining the offset under Section 4.2(a), Section 4.2(b) and
              such person's SERP Side Letter for such person's Pension Plan
              benefit, to the extent otherwise applicable, shall be computed by
              including the additional years of age and service credit which
              were (or will be) taken into account, pursuant to the provisions
              of Section 5.5(i)(a)(3) of such Participant's employment agreement
              with the Company, in computing the amount of the lump sum payment
              made (or to be made) to such Participant in lieu of an actual
              increase in such Participant's benefit under the Pension Plan.

         (h) If that Covered Participant whose social security number is
[Christopher Havens] remains employed with UDS on the Change in Control Date,
determined without regard to the foregoing subsection (e), such person shall
receive a lump sum payment of $500,000 upon the earlier of:

         (i)  such person's "involuntary termination, other than for Cause," as
              those terms are defined under the employment agreement between
              such person and the Company; provided, however, that an
              "involuntary termination" shall not be deemed to have occurred for
              purposes of this clause (i) in the event that such person
              voluntarily terminates employment on account of a significant
              reduction, occurring not later than the Change in Control Date, in
              such person's duties or the addition, occurring not later than the
              Change in Control Date, of duties which, in either case, are
              materially inconsistent with such person's then title or position,
              such that no amount shall be paid pursuant to this subsection (h)
              to such person; and further, provided, however, that an
              "involuntary termination" shall be deemed to have occurred for
              purposes of this clause (i) in the event that such person
              voluntarily terminates employment on account of a significant
              reduction, occurring subsequent to the Change in Control Date, in
              such person's duties or the addition, occurring subsequent to the
              Change in Control Date, of duties which, in either case, are
              materially inconsistent with such person's title or position as in
              effect on the Change in Control Date, such that an amount shall be
              paid pursuant to this subsection (h) to such person, or

         (ii) twelve months following the Change in Control Date, provided such
              person is still employed by UDS on such date.

No amount shall be payable pursuant to this subsection (h) in the event that
such Covered Participant terminates employment prior to the date set forth in
the foregoing clause (ii) for any reason not described in the foregoing clause
(i).



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         Any amount otherwise payable pursuant to this subsection (h) to such
Covered Participant (i) shall not be reduced by any amounts previously paid to
such person pursuant to any other provision of the SERP and (ii) shall be
disregarded in determining the amount of any future benefits otherwise payable
to such person pursuant to any other provision of the SERP.

         (i) Notwithstanding any other provision of the SERP to the contrary, to
the extent that any subsequent amendment to this Section 15 would adversely
affect the determination of any particular Covered Participant's SERP benefit,
such amendment shall be effective with respect to such person only if such
person consents, in writing, to the application of such amendment, other than an
amendment to subsection (f) of this Section 15, as to which the consent of
Covered Participants shall not be required.




                                    Ultramar Diamond Shamrock Corporation


                                    By:



                                    Accepted and agreed to with respect to the
                                    calculation of their benefits under the
                                    Ultramar Corporation Supplemental Retirement
                                    Plan


                                    By:
                                       ---------------------------------
                                        Jean Gaulin


                                    By:
                                       ---------------------------------
                                        Christopher Havens


                                    By:
                                       ---------------------------------
                                        H. Pete Smith