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                                                                   EXHIBIT 10.21

                              EMPLOYMENT AGREEMENT

            This EMPLOYMENT AGREEMENT (the "Agreement"), dated as of November
27, 1996, but effective as provided herein, is made and entered into by and
between Ultramar Corporation, a Delaware corporation (the "Company"), and
Christopher Havens (the "Executive").

            WHEREAS, the Executive has been serving as a senior executive
officer of Ultramar Energy Inc., a Delaware corporation and a direct wholly
owned subsidiary of the Company ("Ultramar Energy Inc.");

            WHEREAS, the Executive is a party to an Employment Agreement with
Ultramar Corporation, dated as of March 15, 1994 (the "Prior Agreement");

            WHEREAS, pursuant to the Agreement and Plan of Merger between
Ultramar Corporation and Diamond Shamrock, Inc., a Delaware corporation
("Diamond Shamrock, Inc."), dated as of September 22, 1996 (the "Merger
Agreement"), as of the effective time of the Merger (the "Effective Date"),
Diamond Shamrock, Inc. will be merged with and into Ultramar Corporation, with
Ultramar Corporation as the surviving entity (the "Merger");

            WHEREAS, pursuant to the Merger Agreement, the Company is authorized
to enter into this Agreement with Executive;

            WHEREAS, the Company considers it in the best interests of its
stockholders to foster the continuous employment of certain key management
personnel;

            WHEREAS, the Company recognizes that, as is the case for most
publicly held companies, the possibility of a Change in Control (as defined
herein) exists;

            WHEREAS, the Company wishes to assure itself of both present and
future continuation of management in light of the Merger and in the event of a
Change in Control subsequent to the Merger;

            WHEREAS, the Company wishes to continue to employ the Executive and
to continue to provide his services to Ultramar Energy Inc., and the Executive
is willing to continue to render services, both on the terms and subject to the
conditions set forth in this Agreement;

            NOW, THEREFORE, in consideration of the promises and of the mutual
covenants herein contained, it is agreed as follows:
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      1. Employment.

            1.1. The Company hereby agrees to continue to employ the Executive
and the Executive hereby agrees to undertake employment with the Company upon
the terms and conditions herein set forth.

            1.2. Employment will be for a term commencing on the Effective Date
and, subject to earlier expiration upon the Executive's termination under
Section 5, expiring three years from the Effective Date (the "Term").
Notwithstanding the previous sentence, this Agreement and the employment of the
Executive will be automatically renewed and the Term extended, subject to
Section 5, for successive one-year periods upon the terms and conditions set
forth herein, commencing on the third anniversary of the Effective Date, and on
each anniversary date thereafter, unless either party to this Agreement gives
the other party written notice (in accordance with Section 12.5) of such party's
intention to terminate this Agreement at least three months prior to the end of
such initial or extended term. For purposes of this Agreement, any reference to
the "Term" of this Agreement will include the original term and any extension
thereof.

      2. Position and Duties.

            2.1. Position and Duties. During the Term, the Executive will serve
as Senior Vice President - U.S. Wholesale and Northeast Retail of the Company,
and will have such duties, functions, responsibilities and authority as are (i)
consistent with the Executive's position as Senior Vice President - U.S.
Wholesale and Northeast Retail of the Company; or (ii) assigned to his office in
the Company's bylaws; or (iii) reasonably assigned to him by the Company's Board
of Directors (the "Board").

            2.2. Commitment. During the Term, the Executive will be the
Company's full-time employee and, except as may otherwise be approved in advance
in writing by the Board, and except during vacation periods and reasonable
periods of absence due to sickness, personal injury or other disability, the
Executive will devote substantially all of his business time and attention to
the performance of his duties to the Company and Ultramar Energy Inc.

      3. Place of Performance. In connection with his employment during the
Term, unless otherwise agreed by the Executive, the Executive will be based at
such location as may be determined by the Board. The Executive will undertake
normal business travel on behalf of the Company.


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      4. Compensation and Related Matters.

            4.1. Compensation and Benefits.

                  (i)  Annual Base Salary. During the Term of this Agreement,
the Company will pay to the Executive an annual base salary of not less than
$265,000, which annual base salary may be modified from time to time by the
Board (or the Compensation Committee thereof) in its sole discretion, payable at
the times and in the manner consistent with the Company's general policies
regarding compensation of executive employees. The Board may from time to time
authorize such additional compensation to the Executive, in cash or in property,
as the Board may determine in its sole discretion to be appropriate.

                  (ii) Annual Incentive Compensation. If the Board (or the
Compensation Committee thereof) authorizes any cash incentive compensation or
approves any other management incentive program or arrangement, the Executive
will be eligible to participate in such plan, program or arrangement under the
general terms and conditions applicable to executive and management employees;
provided, however, that so long as the Executive remains employed by the Company
at the end of the applicable fiscal year, (a) the annual cash incentive
compensation paid by the Company to the Executive for the Company's fiscal year
that includes the Effective Date, aggregated with any other annual incentive
compensation earned by the Executive for calendar year 1996, will be in an
amount not less than the greater of (1) 40% of the Executive's highest annual
base salary rate during the fiscal year to which such incentive compensation
relates, and (2) the Executive's actual annual incentive compensation earned
during such fiscal year, as determined by the Company's Board (or the
Compensation Committee thereof), and (b) the cash incentive compensation paid to
the Executive for the Company's next succeeding fiscal year will be in an amount
not less than the greater of (1) 40% of the Executive's highest annual base
salary rate during the fiscal year to which such incentive compensation relates,
and (2) the Executive's actual annual incentive compensation during such fiscal
year, as determined by the Board (or the Compensation Committee thereof). Except
as set forth in the proviso to the preceding sentence, nothing in this Section
4.1(ii) will guarantee to the Executive any specific amount of incentive
compensation, or prevent the Board (or the Compensation Committee thereof) from
establishing performance goals and compensation targets applicable only to the
Executive.

            4.2. Executive Benefits. In addition to the compensation described
in Section 4.1, the Company will make


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available to the Executive and his eligible dependents, subject to the terms and
conditions of the applicable plans, including without limitation the eligibility
rules, participation in all Company-sponsored employee benefit plans including
all employee retirement income and welfare benefit policies, plans, programs or
arrangements in which senior executives of the Company participate, including
any stock option, stock purchase, stock appreciation, savings, pension,
supplemental executive retirement or other retirement income or welfare benefit,
disability, salary continuation, and any other deferred compensation, incentive
compensation, group and/or executive life, health, medical/hospital or other
insurance (whether funded by actual insurance or self-insured by the Company),
expense reimbursement or other employee benefit policies, plans, programs or
arrangements or any equivalent successor policies, plans, programs or
arrangements that may now exist or be adopted hereafter by the Company.

            4.3. Expenses. The Company will promptly reimburse the Executive for
all travel and other business expenses the Executive incurs in order to perform
his duties to the Company and Ultramar Energy Inc. under this Agreement in a
manner commensurate with the Executive's position and level of responsibility
with the Company, and in accordance with the Company's policy regarding
substantiation of expenses.

      5. Termination. Notwithstanding the Term specified in Section 1.2, the
termination of the Executive's employment hereunder will be governed by the
following provisions:

            5.1. Death. In the event of the Executive's death during the Term,
the Company will pay to the Executive's beneficiaries or estate, as appropriate,
promptly after the Executive's death, (i) the unpaid annual base salary to which
the Executive is entitled, pursuant to Section 4.1, through the date of the
Executive's death, and (ii) for any accrued but unused vacation days, to the
extent and in the amounts, if any, provided under the Company's usual policies
and arrangements. This Section 5.1 will not limit the entitlement of the
Executive's estate or beneficiaries to any death or other benefits then
available to the Executive under any life insurance, stock ownership, stock
options, or other benefit plan or policy that is maintained by the Company for
the Executive's benefit.

            5.2. Disability.

                  (i) If the Company determines in good faith that the Executive
has incurred a Disability (as defined below) during the Term, the Company may
give the Executive written notice of its intention to terminate the Executive's
employment.


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In such event, the Executive's employment with the Company will terminate
effective on the 30th day after receipt of such notice by the Executive,
provided that within the 30 days after such receipt, the Executive will not have
returned to full-time performance of his duties. The Executive will continue to
receive his annual base salary and benefits until the date of termination. In
the event of the Executive's Disability, the Company will pay the Executive,
promptly after the Executive's termination, (a) the unpaid annual base salary to
which he is entitled, pursuant to Section 4.1, through the date of the
Executive's termination, (b) for any accrued but unused vacation days, to the
extent and in the amounts, if any, provided under the Company's usual policies
and arrangements, and (c) a lump sum in cash in an amount equal to 50% of his
annual base salary at the time of termination. This Section 5.2 will not limit
the entitlement of the Executive, the Executive's estate or beneficiaries to any
disability or other benefits then available to the Executive under any
disability insurance or other benefit plan or policy that is maintained by the
Company for the Executive's benefit.

                  (ii) For purposes of this Agreement, "Disability" will mean
the Executive's incapacity due to physical or mental illness substantially to
perform his duties on a full-time basis for six consecutive months and within
30 days after a notice of termination is thereafter given by the Company the
Executive will not have returned to the full-time performance of the
Executive's duties; provided, however, if the Executive disagrees with a
determination to terminate him because of Disability, the question of the
Executive's disability will be subject to the certification of a qualified
medical doctor agreed to by the Company and the Executive or, in the event of
the Executive's incapacity to designate a doctor, the Executive's legal
representative. In the absence of agreement between the Company and the
Executive, each party will nominate a qualified medical doctor and the two
doctors will select a third doctor, who will make the determination as to
Disability. In order to facilitate such determination, the Executive will, as
reasonably requested by the Company, (a) make himself available for medical
examinations by a doctor in accordance with this Section 5.2(ii), and (b) grant
the Company and any such doctor access to all relevant medical information
concerning him, arrange to furnish copies of medical records to such doctor and
use his best efforts to cause his own doctor to be available to discuss his
health with such doctor.


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<PAGE>

            5.3. Cause.

                  (i)  The Company may terminate the Executive's employment
hereunder for Cause (as defined below). In the event of the Executive's
termination for Cause, the Company will promptly pay to the Executive (or his
representative) the unpaid annual base salary to which he is entitled, pursuant
to Section 4.1, through the date the Executive is terminated and the Executive
will be entitled to no other compensation, except as otherwise due to him under
applicable law.

                  (ii) For purposes of this Agreement, the Company will have
"Cause" to terminate the Executive's employment hereunder upon a finding by the
Board that (a) the Executive committed an illegal act or acts that were intended
to and did defraud the Company, (b) the Executive engaged in gross negligence
or gross misconduct against the Company or another employee, or in carrying out
his duties and responsibilities, or (c) the Executive materially breached any of
the express covenants set forth in Section 9.1, 9.2 or 9.3. The Company will not
have Cause unless and until the Company provides the Executive with written
notice that the Company intends to terminate his employment for Cause. Such
written notice will specify the particular act or acts, or failure to act, that
is or are the basis for the decision to so terminate the Executive's employment
for Cause. The Employee will be given the opportunity within 30 calendar days of
the receipt of such notice to meet with the Board to defend such act or acts, or
failure to act. The Executive's employment by the Company automatically will be
terminated under this Section 5.3 for Cause as of the receipt of the written
notice from the Company or, if later, the date specified in such notice. A
notice given under this Section 5.3 must set forth in reasonable detail the
facts and circumstances claimed to provide a basis for termination of the
Executive's employment for Cause, and if the termination date is other than the
date of receipt of such notice, specify the date on which the Executive's
employment is to be terminated (which date will not be earlier than the date on
which such notice is given in accordance with Section 13.5). Such notice must be
given no later than 180 business days after a director of the Company (excluding
the Executive, i f applicable) first has actual knowledge of the events
justifying the purported termination.

            5.4. Termination.

                  (i)  Involuntary Termination. The Executive's employment
hereunder may be terminated by the Company for any reason by written notice as
provided in Section 12.5. The Executive will be treated for purposes of this
Agreement as having been involuntarily terminated by the Company other than


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for Cause if the Executive terminates his employment with the Company for any of
the following reasons (each, a "Good Reason"): without the Executive's written
consent, (a) the Company has breached any material provision of this Agreement
and within 30 days after notice thereof from the Executive, the Company fails to
cure such breach; (b) a successor or assign (whether direct or indirect, by
purchase, merger, consolidation or otherwise) to all or substantially all of the
business and/or assets of the Company fails to assume liability under the
Agreement; (c) at any time after the Company has notified the Executive pursuant
to Section 1.2 that the Company does not intend to renew the Agreement and the
Executive's employment at the end of the Term (including any previous renewals)
(rather than to allow the Agreement automatically to renew); (d) a material
reduction in the aggregate benefits described by Section 4.2 (other than
stock-based compensation) provided to the Executive, unless such decrease is
required by law or is applicable to all employees of the Company eligible to
participate in any employee benefit arrangement affected by such reduction; (e)
a significant reduction in the Executive's duties or the addition of duties,
which in either case are materially inconsistent with the Executive's title or
position; (f) a reduction in the Executive's annual base salary or (g) provided
that the Executive has relocated to the location of the Company's principal
place of business prior to Jean Gaulin becoming Chief Executive Officer of the
Company, for any reason or without reason within 120 days after (1) the
termination of the employment of Mr. Gaulin prior to January 1, 1999, without
Mr. Gaulin becoming Chief Executive Officer of the Company if such termination
of employment is involuntary without "Cause" or voluntary with "Good Reason"
under the terms of Mr. Gaulin's employment agreement with the Company, or (2)
January 1, 1999, if Mr. Gaulin has not become the Chief Executive Officer of the
Company by such date.

                  (ii) Voluntary Termination. The Executive may voluntarily
terminate the Agreement at any time by notice to the Company as provided in
Section 12.5. The Executive's death or Disability (as defined in Section
5.2(ii)) during the term of the Agreement will constitute a voluntary
termination of employment for purposes of eligibility for termination payments
and benefits as provided in Section 5.5, but for no other purpose.

            5.5. Termination Payments and Benefits.

                  (i)  Form and Amount. Upon the Executive's involuntary
termination, other than for Cause, (a) subject to Section 5.5(iii), the Company
will pay or provide to the Executive (1) his annual base salary and benefits
until the date of termination, (2) within five business days after termination
of his employment, a lump sum cash payment equal in amount to


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three times the sum of (x) the Executive's highest annual base salary in effect
during the three years prior to his date of termination, and (y) the highest
annual incentive compensation earned by the Executive during the same
three-year period, (3) three additional years of age and service credit under
the qualified and nonqualified defined benefit retirement plans of the Company
in which the Executive participates at the time of termination; provided,
however, that in the case of a qualified defined benefit pension plan, the
present value of the additional benefit the Executive would have accrued if he
had been credited for all purposes with the additional years of age and service
under such plan as of the Executive's date of termination with the Company will
be paid in a lump sum in cash within five business days after termination of the
Executive's employment, and (4) for a period of one year after termination of
his employment, the continuation of the employee welfare benefits set forth in
Section 4.2 except as offset by benefits paid by other sources as set forth in
Section 8, or as prohibited by law or as a condition of maintaining the
tax-favored status of any such benefits to the Company or its employees; (b) the
Executive's benefit under the applicable supplemental executive retirement plan
will be not less than the benefit the Executive would have received under the
terms of the corresponding plan (including any individual modifications thereof)
applicable to the Executive as in effect immediately prior to the Effective Date
determined as if the Executive had continued employment under the terms of such
corresponding plan (and modifications) until his actual termination of
employment; and (c) if the Executive had theretofore relocated to San Antonio
and his employment has been terminated within two years after the Effective
Date, Executive will be reimbursed the costs of relocation from San Antonio to
any other location in the continental United States under the same policies and
procedures applicable to Executive's reimbursement for relocation to San
Antonio.

                  (ii)  Maintenance of Benefits. During the period set forth in
Section 5.5(i) (a) (4), the Company will use its best efforts to maintain in
full force and effect for the continued benefit of the Executive all referenced
benefits or will arrange to make available to the Executive benefits
substantially similar to those that the Executive would otherwise have been
entitled to receive if his employment had not been terminated. Such benefits
will be provided to the Executive on the same terms and conditions (including
employee contributions toward the premium payments) under which the Executive
was entitled to participate immediately prior to his termination.

                  (iii) Release. No benefit will be paid or made available under
Section 5.5(i) (a) unless the Executive first executes a release in the form
attached as an exhibit to this


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Agreement, and (b) to the extent any portion of such release is subject to the
seven-day revocation period prescribed by the Age Discrimination in Employment
Act of 1967, as amended, or to any similar revocation period in effect on the
date of termination of Executive's employment, such revocation period has
expired.

      6. Change in Control Provisions.

            6.1. Impact of Change in Control. In the event of a "Change in
Control" of the Company, as defined in Section 6.2, (i) the Company will cause
all cash benefits due under this Agreement to be secured by an irrevocable trust
for the benefit of the Executive, the assets of which will be subject to the
claims of the Company's creditors, and will transfer to such trust cash and
other property adequate to satisfy all of the expenses of the trust for at least
five years after the Change in Control and any of the Company's actual and
potential cash obligations under this Agreement, (ii) if the Executive's
employment is involuntarily terminated without Cause after the Change in
Control, (A) the covenants of Sections 9.1 and 10 will be inapplicable to the
Executive, and (B) the covenant of Section 9.2 will expire on the third
anniversary of the date of termination of the Executive's employment, and (iii)
the definition of Good Reason, as set forth in Section 5.4(i) above, will be
expanded to include the following:

                  (a) A good faith determination by the Executive that, as a
result of the Change in Control and a change in circumstances thereafter
significantly affecting his positions, including a change in the scope of
business or other activities for which he was responsible, he has been rendered
substantially unable to carry out, has been substantially hindered in the
performance of, or has suffered a substantial reduction in, any of the
authorities, powers, functions, responsibilities or duties attached to any of
the Executive's positions; the Executive's determination will be presumed to
have been made in good faith unless otherwise shown by the Company by clear and
convincing evidence;

                  (b) The relocation of the Company's principal executive
offices (but only if, immediately prior to the Change in Control, the
Executive's principal place of employment was at the Company's principal
executive offices), or requirement that the Executive have as his principal
location of work any location that is, in excess of 50 miles from the location
thereof immediately preceding the Change in Control or to travel away from his
home or office significantly more often that required immediately prior to the
Change in Control; or


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                  (c)   For any reason, or without reason, during the 30-day
period immediately following the first anniversary of the first occurrence of a
Change in Control.

            6.2. Definition of Change in Control. For purposes of this
Agreement, a "Change in Control" will be deemed to occur if at any time during
the term of the Agreement any of the following events will occur:

                  (i)   The Company is merged, consolidated or reorganized into
or with another corporation or other legal person, and as a result of such
merger, consolidation or reorganization, less than 50% of the combined voting
power of the then-outstanding securities of such corporation or person
immediately after such transaction are held in the aggregate by the holders of
Voting Stock (as that term is hereafter defined) of the Company immediately
prior to such transaction;

                  (ii)  The Company sells or otherwise transfers all or
substantially all of its assets to any other corporation or other legal person,
and as a result of such sale or transfer, less than 50% of the combined voting
power of the then-outstanding voting securities of such corporation or person
are held in the aggregate by the holders of Voting Stock of the Company
immediately prior to such sale;

                  (iii) There is a report filed on Schedule 13D or Schedule
14D-1 (or any successor schedule, form or report), each as promulgated pursuant
to the Securities Exchange Act of 1934 (the "Exchange Act"), disclosing that any
person (as the term "person" is used in Section 13(d) (3) or Section 14(d) (2)
of the Exchange Act) has become the beneficial owner (as the term "beneficial
owner" is defined under Rule 13d-3 or any successor rule or regulation
promulgated under the Exchange Act) of securities representing 20% or more of
the combined voting power of the then-outstanding securities of the Company
entitled to vote generally in the election of Directors of the Company ("Voting
Stock");

                  (iv)  The Company files a report or proxy statement with the
Securities and Exchange Commission pursuant to the Exchange Act disclosing in
response to Form 8-K or Schedule 14A (or any successor schedule, form or report
or item therein) that a change in control of the Company has or may have
occurred or will or may occur in the future pursuant to any then-existing
contract or transaction; or

                  (v)   If during the period of two consecutive years
individuals who at the beginning of any such period constitute the Directors of
the Company cease for any reason to


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constitute at least a majority thereof unless the election, or the nomination
for election by the Company's shareholders, of each Director of the Company
first elected during such period was approved by a vote of at least two-thirds
of the Directors of the Company then still in office who were Directors of the
Company at the beginning of any such period (excluding for this purpose the
election of any new Director in connection with an actual or threatened election
or proxy contest).

Notwithstanding the foregoing provisions of Section 6.2(iii) or (iv) hereof,
unless otherwise determined in a specific case by majority vote of the Board (or
the Compensation Committee thereof), a "Change in Control" will not be deemed to
have occurred for purposes of this Agreement solely because the Company, an
entity in which the Company directly or beneficially owns 50% or more of the
voting securities of such entity, any Company-sponsored employee stock ownership
plan or any other employee benefit plan of the Company either files or becomes
obligated to file a report or a proxy statement under or in response to Schedule
13D, Schedule 14D-1, Form 8-K or Schedule 14A (or any successor schedule, form
or report or item therein) under the Exchange Act, disclosing beneficial
ownership by it of shares of voting securities of the Company, whether in excess
of 20% or otherwise, or because the Company reports that a change in control of
the Company has or may have occurred or will or may occur in the future by
reason of such beneficial ownership. Notwithstanding the foregoing provisions of
Section 6.2, the Merger will not constitute a Change in Control.

      7. Certain Additional Payments by the Company:

                  (i) Anything in this Agreement to the contrary
notwithstanding, if it is determined (as hereafter provided) that any payment or
distribution by the Company to or for the benefit of the Executive, whether paid
or payable or distributed or distributable pursuant to the terms of this
Agreement or otherwise pursuant to or by reason of any other agreement, policy,
plan, program or arrangement, including without limitation any stock option,
stock appreciation right or similar right, or the lapse or termination of any
restriction on or the vesting or exercisability of any of the foregoing (a
"Payment"), would be subject to the excise tax imposed by Section 4999 of the
Code (or any successor provision thereto) by reason of being' contingent on a
change in ownership or control" of the Company, within the meaning of Section
280G of the Code (or any successor provision thereto) or to any similar tax
imposed by state or local law, or any interest or penalties with respect to such
excise tax (such tax or taxes, together with any such interest and penalties,
are hereafter collectively referred to as the "Excise Tax"), then the Executive
will be entitled to receive an


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additional payment or payments (a "Gross-Up Payment") in an amount such that,
after payment by the Executive of all taxes (including any interest or penalties
imposed with respect to such taxes), including any 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. No Gross-Up Payment will be
made with respect to the Excise Tax, if any, attributable to (a) any incentive
stock option, as defined by Section 422 of the Code ("ISO") granted prior to the
execution of this Agreement (unless a comparable Gross-Up Payment has
theretofore been made available with respect to such option), or (b) any stock
appreciation or similar right, whether or not limited, granted in tandem with
any ISO described in clause (a).

                  (ii) Subject to the provisions of Section 7(vi) hereof, all
determinations required to be made under this Section 7, including whether an
Excise Tax is payable by the Executive and the amount of such Excise Tax and
whether a Gross-tip Payment is required and the amount of such Gross-Up
Payment, will be made by a nationally recognized firm of certified public
accountants (the "Accounting Firm") selected by the Executive in his sole
discretion. The Executive will direct the Accounting Firm to submit its
determination and detailed supporting calculations to both the Company and the
Executive within 15 calendar days after the Termination Date, if applicable, and
any other such time or times as may be requested by the Company or the
Executive. If the Accounting Firm determines that any Excise Tax is payable by
the Executive, the Company will pay the required Gross-Up Payment to the
Executive within five business days after receipt of such determination and
calculations. If the Accounting Firm determines that no Excise Tax is payable by
the Executive, it will, at the same time as it makes such determination, furnish
the Executive with an opinion that he has substantial authority not to report
any Excise Tax on his federal, state, local income or other tax return. Any
determination by the Accounting Firm as to the amount of the Gross-Up Payment
will be binding upon the Company and the Executive. As a result of the
uncertainty in the application of Section 4999 of the Code (or any successor
provision thereto) and the possibility of similar uncertainty regarding
applicable state or local tax law at the time of any 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 (an "Underpayment"),
consistent with the calculations required to be made hereunder. In the event
that the Company exhausts or fails to pursue its remedies pursuant to .Section
7(vi) hereof and the Executive thereafter is required to make a payment of any
Excise Tax, the Executive will direct the Accounting Firm to determine the
amount of the Underpayment that has occurred and to submit its determination and
detailed


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supporting calculations to both the Company and the Executive as promptly as
possible. Any such Underpayment will be promptly paid by the Company to, or for
the benefit of, the Executive within five business days after receipt of such
determination and calculations.

                  (iii) The Company and the Executive will each provide the
Accounting Firm access to and copies of any books, records and documents in the
possession of the Company or the Executive, as the case may be, reasonably
requested by the Accounting Firm, and otherwise cooperate with the Accounting
Firm in connection with the preparation and issuance of the determination
contemplated by Section 7(ii) hereof.

                  (iv)  The federal, state and local income or other tax returns
filed by the Executive will be prepared and filed on a consistent basis with the
determination of the Accounting Firm with respect to the Excise Tax payable by
the Executive. The Executive will make proper payment of the amount of any
Excise Tax, and at the request of the Company, provide to the Company true and
correct copies (with any amendments) of his federal income tax return as filed
with the Internal Revenue Service and corresponding state and local tax returns,
if relevant, as filed with the applicable taxing authority, and such other
documents reasonably requested by the Company, evidencing such payment. If prior
to the filing of the Executive's federal income tax return, or corresponding
state or local tax return, if relevant, the Accounting Firm determines that the
amount of the Gross-Up Payment should be reduced, the Executive will within five
business days pay to the Company the amount of such reduction.

                  (v)   The fees and expenses of the Accounting Firm for its
services in connection with the determinations and calculations contemplated by
Sections 7(ii) and (iv) hereof will be borne by the Company. If such fees and
expenses are initially advanced by the Executive, the Company will reimburse the
Executive the full amount of such fees and expenses within five business days
after receipt from the Executive of a statement therefor and reasonable evidence
of his payment thereof.

                  (vi)  The Executive will notify the Company in writing of any
claim by the Internal Revenue Service that, if successful, would require the
payment by the Company of a Gross-up Payment. Such notification will be given
as promptly as practicable but no later than 10 business days after the
Executive actually receives notice of such claim and the Executive will further
apprise the Company of the nature of such claim and the date on which such claim
is requested to be paid (in each case, to the extent known by the Executive) .
The


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Executive will not pay such claim prior to the earlier of (a) the expiration of
the 30-calendar-day period following the date on which he gives such notice to
the Company and (b) the date that any payment of amount with respect to such
claim is 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
will:

                        (1) provide the Company with any written records or
                  documents in his possession relating to such claim reasonably
                  requested by the Company;

                        (2) take such action in connection with contesting such
                  claim as the Company will reasonably request in writing from
                  time to time, including without limitation accepting legal
                  representation with respect to such claim by an attorney
                  competent in respect of the subject matter and reasonably
                  selected by the Company;

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

                        (4) permit the Company to participate in any proceedings
                  relating to such claim;

provided, however, that the Company will bear and pay directly all costs and
expenses (including interest and penalties) incurred in connection with such
contest and will indemnify and hold harmless the Executive, on an after-tax
basis, for and against any Excise Tax or income tax, including interest and
penalties with respect thereto, imposed as a result of such representation and
payment of costs and expenses. Without limiting the foregoing provisions of this
Section 7(vi), the Company will control all proceedings taken in connection with
the contest of any claim contemplated by this Section 7(vi) 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
(provided, however, that the Executive may participate therein at his own cost
and expense) and may, at its 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 will determine; provided, however, that if o
the Company directs the Executive to pay the tax claimed and sue for a refund,
the Company will advance the amount of such payment to the Executive on an
interest-free basis and will indemnify and hold the Executive harmless, on an
after-tax basis, from any


                                       14
<PAGE>

Excise Tax or income tax, including interest or penalties with respect thereto,
imposed with respect to such advance; and provided further, however, that any
extension of the statute of limitations relating to payment of taxes for the
taxable year of the Executive with respect to which the contested amount is
claimed to be due is limited solely to such contested amount. Furthermore, the
Company's control of any such contested claim will be limited to issues with
respect to which a Gross-Up Payment would be payable hereunder and the Executive
will 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.

                  (vii) If, after the receipt by the Executive of an amount
advanced by the Company pursuant to Section 7(vi) hereof, the Executive receives
any refund with respect to such claim, the Executive will (subject to the
Company's complying with the requirements of Section 7(vi) hereof) promptly pay
to the Company the amount of such refund (together with any interest paid or
credited thereon after any taxes applicable thereto). If, after the receipt by
the Executive of an amount advanced by the Company pursuant to Section 7(vi)
hereof, a determination is made that the Executive will 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 or refund prior to the
expiration of 30 calendar days after such determination, then such advance will
be forgiven and will not be required to be repaid and the amount of such advance
will offset, to the extent thereof, the amount of Gross-Up Payment required to
be paid pursuant to this Section 7.

      8. Mitigation and Offset. The Executive is under no obligation to mitigate
damages or the amount of any payment or benefit provided for hereunder by
seeking other employment or otherwise; provided, however, that the Executive's
coverage under the Company's welfare benefit plans will be reduced to the extent
that the Executive becomes covered under any comparable employee benefit plan
made available by another employer and covering the same type of benefits. The
Executive will report to the Company any such benefits actually received by him.

      9. Competition; Confidentiality; Nonsolicitation.

            9.1. (i)    Subject to Section 6.1(ii), the Executive hereby
covenants and agrees that during the Term and for one year following the Term he
will not, without the prior written consent of the Company, engage in
Competition (as defined below) with the Company. For purposes of this Agreement,
if the Executive takes any of the following actions he will be engaged in
"Competition" engaging in or carrying on, directly or indirectly, any


                                       15
<PAGE>

enterprise, whether as an advisor, principal, agent, partner, officer, director,
employee, stockholder, associate or consultant to any person, partnership,
corporation or any other business entity, that is principally engaged in the
business of refining and/or marketing oil or related products within the
territory of the Province of Quebec; provided, however, that "Competition" will
not include (a) the mere ownership of securities in any enterprise and exercise
of rights appurtenant thereto or (b) participation in management of any
enterprise or business operation thereof other than in connection with the
competitive operation of such enterprise.

                  (ii) Subject to Section 6.1(ii), the Executive hereby
covenants and agrees that during the Term and for three years following the Term
he will not assist a third party in preparing or making an unsolicited bid for
the Company, engaging in a proxy contest with the Company, or engaging in any
other similar activity.

            9.2. During the Term, the Company agrees that it will disclose to
Executive its confidential or proprietary information (as defined in this
Section 9.2) to the extent necessary for Executive to carry out his obligations
under this Agreement. Subject to Section 6.1(ii), the Executive hereby covenants
and agrees that he will not, without the prior written consent of the Company,
during the Term or thereafter disclose to any person not employed by the
Company, or use in connection with engaging in Competition with the Company, any
confidential or proprietary information of the Company. For purposes of this
Agreement, the term "confidential or proprietary information" will include all
information of any nature and in any form that .is owned by the Company and that
is not publicly available or generally known to persons engaged in businesses
similar or related to those of the Company. Confidential information will
include, without limitation, the Company's financial matters, customers,
employees, industry contracts, and all other secrets and all other information
of a confidential or proprietary nature. The foregoing obligations imposed by
this Section 9.2 will cease if such confidential or proprietary information will
have become, through no fault of the Executive, generally known to the public or
the Executive is required by law to make disclosure (after giving the Company
notice and an opportunity to contest such requirement).

            9.3. The Executive hereby covenants and agrees that during the Term
and for one year thereafter he will not attempt to influence, persuade or
induce, or assist any other person in so persuading or inducing, any employee of
the Company to give up, or to not commence, employment or a business
relationship with the Company.


                                       16
<PAGE>

            9.4. For purposes of the second sentence of Section 9.1(i), the
second and third sentences of Section 9.2, and Section 9.3 in its entirety, the
term "Company" will refer to both the Company and Ultramar Energy Inc.

            9.5. Executive acknowledges and agrees that the remedy at law
available to the Company for breach of any of his post-termination obligations
under Sections 9.1, 9.2 and 9.3 would be inadequate and that damages flowing
from such a breach may not readily be susceptible to being measured in monetary
terms. Accordingly, Executive acknowledges, consents and agrees that, in
addition to any other rights or remedies which the Company may have at law, in
equity or under this Agreement, upon adequate proof of his violation of any such
provision of this Agreement, the Company will be entitled to immediate
injunctive relief and may obtain a temporary order restraining any threatened or
further breach, without the necessity of proof of actual damage.

      10. Post-termination Assistance. Subject to Section 6.1(ii), the Executive
agrees that after his employment with the Company has terminated he will
provide, upon reasonable notice, such information and assistance to the Company
as may reasonably be requested by the Company in connection with any audit,
governmental investigation or litigation in which it or any of its affiliates is
or may become a party; provided, however, that (i) the Company agrees to
reimburse the Executive for any related out-of-pocket expenses, including
travel expenses, and to pay the Executive reasonable compensation for his time
based on his rate of annual salary at the time of termination and (ii) any such
assistance may not unreasonably interfere with the then-current employment of
the Executive.

      11. Survival. The expiration or termination of the Term will not impair
the rights or obligations of any party hereto that accrue hereunder prior to
such expiration or termination, except to the extent specifically stated herein.
In addition to the foregoing, the Executive's covenants contained in Sections
9.1, 9.2, 9.3 and 10 and the Company's obligations under Sections 5, 7 and 12.1
will survive the expiration or termination of Executive's employment.

      12. Miscellaneous Provisions.

            12.1. Legal Fees and Expenses. Without regard to o whether the
Executive prevails, in whole or in part, in connection therewith, the Company
will pay and be financially responsible for 100% of any and all attorneys' and
related fees and expenses incurred by the Executive in connection with any


                                       17
<PAGE>

dispute associated with the interpretation, enforcement or defense of the
Executive's rights under this Agreement by litigation or otherwise; provided
that, in regard to such dispute, the Executive has not acted in bad faith or
with no colorable claim of success. All such fees and expenses will be paid by
the Company as incurred by the Executive on a monthly basis upon an undertaking
by the Executive to repay such advanced amounts if a court determines, in a
decision against which no appeal may be taken or with respect to which the time
period to appeal has expired, that he acted in bad faith or with no colorable
claim of success.

            12.2. Binding on Successors. This Agreement will be binding upon and
inure to the benefit of the Company, the Executive and each of their respective
successors, assigns, personal and legal representatives, executors,
administrators heirs, distributees, devisees, and legatees, as applicable.

            12.3. Governing Law. This Agreement will be governed, construed,
interpreted and enforced in accordance with the substantive laws of the State of
Delaware, without regard to conflicts of law principles.

            12.4. Severability. Any provision of this Agreement that is deemed
invalid, illegal or unenforceable in any jurisdiction will, as to that
jurisdiction, be ineffective to the extent of such invalidity, illegality or
unenforceability, without affecting in any way the remaining provisions hereof
in such jurisdiction or rendering that or any other provisions of this Agreement
invalid, illegal, or unenforceable in any other jurisdiction. If any covenant
should be deemed invalid, illegal or unenforceable because its scope is
considered excessive, such covenant will be modified so that the scope of the
covenant is reduced only to the minimum extent necessary to render the modified
covenant valid, legal and enforceable.

            12.5. Notices. For all purposes of this Agreement, all
communications, including without limitation notices, consents, requests or
approvals, required or permitted to be given hereunder will be in writing and
will be deemed to have been duly given when hand delivered or dispatched by
electronic facsimile transmission (with receipt thereof confirmed), or five
business days after having been mailed by United States registered or certified
mail, return receipt requested, postage prepaid, or three business days after
having been sent by a nationally recognized overnight courier service such as
Federal Express, UPS, or Purolator, addressed to the Company (to the attention
of the Secretary of the Company) at its principal executive offices and to the
Executive at his principal residence, or to such other address as any party may
have


                                       18
<PAGE>

furnished to the other in writing and in accordance herewith, except that
notices of changes of address will be effective only upon receipt.

                  (i)  To The Company. If to the Company, addressed to the
attention of General Counsel at 9830 Colonnade Boulevard, San Antonio, Texas
78230.

                  (ii) To the Executive. If to the Executive, to him in care of
the Company at the above address.

            12.6. Counterparts. This Agreement may be executed in several
counterparts, each of which will be deemed to be an original, but all of which
together will constitute one and the same Agreement.

            12.7. Entire Agreement. The terms of this Agreement are intended by
the parties to be the final expression of their agreement with respect to the
Executive's employment by the Company and may not be contradicted by evidence of
any prior or contemporaneous agreement. The parties further intend that this
Agreement will constitute the complete and exclusive statement of its terms and
that no extrinsic evidence whatsoever may be introduced in any judicial,
administrative or other legal proceeding to vary the terms of this Agreement.

            12.8. Amendments; Waivers. This Agreement may not be modified,
amended, or terminated except by an instrument in writing, approved by the
Company and signed by the Executive and the Company. Failure on the part of
either party to complain of any action or omission, breach or default on the
part of the other party, no matter how long the same may continue, will never be
deemed to be a waiver of any rights or remedies hereunder, at law or in equity.
The Executive or the Company may waive compliance by the other party with any
provision of this Agreement that such other party was or is obligated to comply
with or perform only through an executed writing; provided, however, that such
waiver will not operate as a waiver of, or estoppel with respect to, any other
or subsequent failure.

            12.9. No Inconsistent Actions. The parties will not voluntarily
undertake or fail to undertake any action or course of action that is
inconsistent with the provisions or essential intent of this Agreement.
Furthermore, it is the intent of the parties hereto to act in a fair and
reasonable manner with respect to the interpretation and application of the
provisions of this Agreement.

            12.10. Headings and Section References. The headings used in this
Agreement are intended for convenience or reference


                                       19
<PAGE>

only and will not in any manner amplify, limit, modify or otherwise be used in
the construction or interpretation of any provision of this Agreement. All
section references are to sections of this Agreement, unless otherwise noted.

      13. Effectiveness and Prior Agreement. This Agreement will become
effective upon, and the Prior Agreement will terminate immediately prior to, the
Effective Date. Notwithstanding any other provision of this Agreement, if the
Merger Agreement is terminated prior to the Effective Date, this Agreement will
have no further force or effect, and the Prior Agreement will continue in effect
as though this Agreement had not been entered into.

            IN WITNESS WHEREOF, the parties have executed this Agreement as of
the date and year first above written but effective as provided in Section 13.

                                      /s/ Christopher Havens
                                      --------------------------
                                      Christopher Havens


                                      ULTRAMAR CORPORATION,
                                      a Delaware corporation

                                      By: /s/ Jean Gaulin
                                         -----------------------
                                          Jean Gaulin
                                          Chief Executive Officer


                                      20
<PAGE>

                                     Exhibit

                          GENERAL RELEASE OF ALL CLAIMS

      This General Release of all Claims (this "Agreement") is entered into by
and between ______________ ("Executive") and Ultramar Diamond Shamrock
Corporation (including its subsidiaries) (collectively the "Company") effective
as of _______ .


      In consideration of the promises set forth in the employment agreement
between Executive and the Company, dated ____________ 1996, as amended as of the
effective date hereof (the "Employment Agreement"), as well as any promises set
forth in this Agreement, Executive and the Company agree as follows:

(1)   Employment Agreement Entitlements

       The Company will provide Executive the post-termination payments and
       benefits to which he is entitled under the Employment Agreement.

(2)   Return of Property

      All Company files, access keys, desk keys, ID badges and credit cards, and
      such other property of the Company as the Company may reasonably request,
      in Executive's possession must be returned no later than the date of
      Executive's termination from the Company (the "Termination Date")

(3)   General Release and Waiver of Claims

      Except as provided in the last sentence of this paragraph (3), Executive
      hereby unconditionally and forever releases, discharges and waives any and
      all claims of any nature whatsoever, whether legal, equitable or
      otherwise, which Executive may have against the Company arising at any
      time on or before the Termination Date, other than with respect to the
      obligations of the Company to the Executive under the Employment
      Agreement. This release of claims extends to any and all claims of any
      nature whatsoever, other than with respect to the obligations of the
      Company to the Executive under the Employment Agreement, whether known,
      unknown or capable or incapable of being known as of the Termination Date
      of thereafter. This Agreement is a release of all claims of any nature
      whatsoever by Executive against the Company, other than with respect to
      the obligations of the Company to the Executive under the Employment
      Agreement, and


                                       21
<PAGE>

      includes, other than as herein provided, any and all claims, demands,
      causes of action, liabilities whether known or unknown including those
      caused by, arising from or related to Executive's employment relationship
      with the Company including, but without limitation, any and all alleged
      discrimination or acts of discrimination which occurred or may have
      occurred on or before the Termination Date based upon race, color, sex,
      creed, national origin, age, disability or any other violation of any
      Equal Employment Opportunity Law, ordinance, rule, regulation or order,
      including, but not limited to, Title VII of the Civil Rights Act of 1964,
      as amended; the Civil Rights Act of 1991; the Age Discrimination in
      Employment Act, as amended (as further described in Section 7 below); the
      Americans with Disabilities Act; claims under the Employee Retirement
      Income Security Act ("ERISA"); or any other federal, state or local laws
      or regulations regarding employment discrimination or termination of
      employment. This also includes claims for wrongful discharge, fraud, or
      misrepresentation under any statute, rule, regulation or under the common
      law.

      The Executive agrees and understands and knowingly agrees to this release
      because it is his intent in executing this Agreement to forever discharge
      the Company from any and all present, future, foreseen or unforeseen
      causes of action except for the obligations of the Company set forth in
      the Employment Agreement.

      Notwithstanding the foregoing, Executive does not .release, discharge or
      waive any rights to indemnification that he may have under the By--Laws of
      the Company, the laws of the State of Delaware, any indemnification
      agreement between the Executive and the Company or any insurance coverage
      maintained by or on behalf of the Company.

(4)   Release and Waiver of Claims Under the Age Discrimination in Employment
      Act

      Executive acknowledges that the Company encouraged him to consult with an
      attorney of his choosing, and through this Agreement encourages him to
      consult with his attorney with respect to possible claims under the Age
      Discrimination in Employment Act of 1967, as amended ("ADEA") and that
      Executive acknowledges that he understands that the ADEA is a federal
      statute that prohibits discrimination, on the basis of age, in employment,
      benefits, and benefit plans. Executive wishes to waive any and all claims
      under the ADEA that he may have, as of the Termination Date, against the
      Company, its shareholders, employees, or successors and


                                       22
<PAGE>

      hereby waives such claims. Executive further understands that by signing
      this Agreement he is in fact waiving, releasing and forever giving up any
      claim under the ADEA that may have existed on or prior to the Termination
      Date. Executive acknowledges that the Company has informed him that he has
      at his option, twenty-one (21) days in which to sign the waiver of this
      claim under ADEA, and he does hereby knowingly and voluntarily waive said
      twenty-one (21) day period. Executive also understands that he has seven
      (7) days following the Termination Date within which to revoke the release
      contained in this paragraph by providing a written notice of his
      revocation of the release and waiver contained in this paragraph to the
      Company. Executive further understands that this right to revoke the
      release contained in this paragraph relates only to this paragraph and
      does not act as a revocation of any other term of this Agreement.

(5)   Proceedings

      Executive has not filed, and agrees not to initiate or cause to be
      initiated on his behalf, any complaint, charge, claim or proceeding
      against the Company before any local, state or federal agency, court or
      other body relating to his employment or the termination of his
      employment, other than with respect to the obligations of the Company to
      the Executive under the Employment Agreement (each individually, a
      "Proceeding"), and agrees not to voluntarily participate in any
      Proceeding. Executive waives any right he may have to benefit in any
      manner from any relief (whether monetary or otherwise) arising out of any
      Proceeding.

(6)   Remedies

      In the event Executive initiates or voluntarily participates in any
      Proceeding, or if he fails to abide by any of the terms of this Agreement
      or his post-termination obligations contained in the Employment
      Agreement, or if he revokes the ADEA release contained in Paragraph 4 of
      this Agreement within the seven-day period provided under Paragraph 4, the
      Company may, in addition to any other remedies it may have, reclaim any
      amounts paid to him under the termination provisions of the Employment
      Agreement or terminate any benefits or payments that are subsequently due
      under the Employment Agreement, without waiving the release granted
      herein. Executive acknowledges and agrees that the remedy at law
      available to the Company for breach of any of his post-termination
      obligations under the Employment Agreement or his obligations under
      Paragraphs 3, 4, and 5 of this Agreement would be inadequate and that
      damages flowing from


                                       23
<PAGE>

      such a breach may not readily be susceptible to being measured in monetary
      terms. Accordingly, Executive acknowledges, consents and agrees that, in
      addition to any other rights or remedies which the Company may have at
      law, in equity or under this Agreement, upon adequate proof of his
      violation of any such provision of this Agreement, the Company shall be
      entitled to immediate injunctive relief and may obtain a temporary order
      restraining any threatened or further breach, without the necessity of
      proof of actual damage.

      Executive understands that by entering into this Agreement he will be
      limiting the availability of certain remedies that he may have against the
      Company and limiting also his ability to pursue certain claims against the
      Company.

(7)   Severability Clause

      In the event any provision or part of this Agreement is found to be
      invalid or unenforceable, only that particular provision or part so found,
      and not the entire agreement, will be inoperative.

(8)   Non-Admission

      Nothing contained in this Agreement will be deemed or construed as an
      admission of wrongdoing or liability on the part of the Company.

(9)   Governing Law

      This Agreement shall be governed by and construed in accordance with the
      laws of the State of Delaware, applicable to agreements made and to be
      performed in that State; and the parties agree to the jurisdiction of the
      U.S. District Court for the District of Delaware, and agree to appear in
      any action in such courts by service of process by certified mail, return
      receipt requested, at the following addresses:

      To Company:       ULTRAMAR DIAMOND SHAMROCK CORPORATION
                        9830 Colonnade Boulevard
                        San Antonio, Texas 78230

                        and

      To Executive:
                    -------------------------------------

                    -------------------------------------

                    -------------------------------------


                                       24
<PAGE>

THE EXECUTIVE ACKNOWLEDGES THAT HE HAS READ THIS AGREEMENT AND THAT HE FULLY
KNOWS, UNDERSTANDS, AND APPRECIATES ITS CONTENTS, AND THAT HE HEREBY EXECUTES
THE SAME AND MAKES THIS AGREEMENT AND THE RELEASE AND AGREEMENTS PROVIDED FOR
HEREIN VOLUNTARILY AND OF HIS OWN FREE WILL.

      IN WITNESS WHEREOF, the parties have executed this AGREEMENT as of the
date first set forth above.


                                    ----------------------------
                                    Christopher Havens


                                    ULTRAMAR DIAMOND SHAMROCK
                                    CORPORATION,
                                    a Delaware corporation


                                    By:
                                       -------------------------

                                       Name:
                                            --------------------

                                       Title:
                                             -------------------


                                      25