<PAGE>

                                                                  EXHIBIT 4.3.32

THIS WARRANT AND ANY SECURITIES ACQUIRED UPON THE EXERCISE OF THIS WARRANT HAVE
NOT BEEN REGISTERED UNDER: (A) THE SECURITIES ACT OF 1933, AS AMENDED, IN
RELIANCE UPON THE EXEMPTIONS FROM REGISTRATION PROVIDED IN SECTIONS 3 AND 4 OF
SUCH ACT AND/OR REGULATIONS D PROMULGATED THEREUNDER; OR (B) ANY STATE
SECURITIES LAWS IN RELIANCE UPON APPLICABLE EXEMPTIONS THEREUNDER. THESE
SECURITIES MUST BE ACQUIRED FOR INVESTMENT ONLY FOR THE ACCOUNT OF THE INVESTOR
AND MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF REGISTRATION UNDER THE
SECURITIES LAWS OR AN OPINION OF COUNSEL ACCEPTABLE TO THE CORPORATION OR ITS
REPRESENTATIVES THAT SUCH SALE OR TRANSFER WOULD NOT VIOLATE APPLICABLE
SECURITIES LAWS OR REGULATIONS.

Warrant No. ___                                           To Purchase _________
                                                          Shares of Common Stock
                                                          ($0.001 par value)

                      CLASS "AR" WARRANT TO PURCHASE SHARES
                               OF COMMON STOCK OF
                                  PROBEX CORP.
                            (A DELAWARE CORPORATION)

                         PURCHASE PRICE PER SHARE: $0.75

EXPIRATION DATE: 5:00 P.M., DALLAS, TEXAS TIME, ON APRIL 1, 2007

       THIS CERTIFIES that, for value received,


is the registered owner and is entitled, subject to the terms and conditions of
this Warrant, until the Expiration Date, to purchase the number of shares of
common stock, $0.001 par value (the "Common Stock"), of Probex Corp. (the
"Corporation") set forth above from the Corporation at the purchase price set
forth above. The number of shares of Common Stock which may be received upon the
exercise of this Warrant and the price to be paid for each share of Common Stock
are subject to adjustment from time to time as hereinafter set forth.

1.       EXERCISE OF WARRANT. Subject to the provisions hereof, this Warrant may
be exercised in whole or in part until the Expiration Date, by delivery of this
Warrant to the Corporation with the exercise form duly executed and payment of
the purchase price (in cash or by certified or bank cashier's check made payable
to the order of the Corporation) for each share purchased.

2.       CORPORATION'S COVENANTS AS TO COMMON STOCK. Shares deliverable upon the
exercise of this Warrant shall, at delivery, be fully paid and non-assessable,
free from taxes, liens, and charges with respect to their purchase. The
Corporation shall at all times, subject to any required stockholder approvals
pursuant to Section 3.20 of that certain Intercreditor and Security Agreement,
dated as of March 28, 2002, by and among the Corporation and the parties
thereto, reserve and hold available


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Class "AR" Warrant No.
                      ----
Page 2


sufficient shares of Common Stock to satisfy all conversion and purchase rights
of outstanding convertible securities, options and warrants.

3.       METHOD OF EXERCISE; FRACTIONAL SHARES. The purchase rights represented
by this Warrant are exercisable at the option of the registered owner in whole
at any time, or in part, from time to time, within the period specified above;
provided, however, that purchase rights are not exercisable with respect to a
fraction of a share of Common Stock. In lieu of issuing a fraction of a share
remaining after exercise of this Warrant as to all full shares covered hereby or
scrip, the Corporation shall pay therefor cash equal to the same fraction of the
then current Warrant purchase price per share. In case of the exercise of this
Warrant for less than all the shares purchasable, the Corporation shall cancel
this Warrant and execute and deliver a new Warrant of like tenor and date for
the balance of the shares purchasable hereunder.

4.       ADJUSTMENT OF EXERCISE PRICE. If after the date hereof and on or prior
to the date of the second anniversary of the payment in full of that certain
promissory note made by the Corporation to the original holder of this Warrant
dated as of February 20, 2001, the Corporation shall (i) issue, (ii) enter into
any binding agreement to issue, or (iii) commence any public or private offering
for the issuance of, shares of Common Stock, warrants to purchase shares of
Common Stock or debt or equity securities that are convertible into shares of
Common Stock, in an aggregate amount of at least 100,000 shares of Common Stock
(excluding any options to purchase Common Stock issued pursuant to any employee
stock option plan of the Corporation), and the issuance, exercise or conversion
price (the "Issuance Price") of such Common Stock is less than $0.75 per share,
then the exercise price per share pursuant to this Warrant shall be adjusted
(and the Corporation shall, after occurrence of any event requiring such
adjustment, notify the holder of this Warrant of the adjustment) so that the
exercise price shall be equal to the Issuance Price. For purposes of this
section, a public or private offering shall be deemed to have commenced if there
is substantial agreement as to the material terms of such offering.

5.       REDEMPTION. The Corporation has no redemption rights pursuant to this
Warrant.


6.       LIMITED RIGHTS OF OWNER. This Warrant does not entitle the owner to any
voting rights or other rights as a shareholder of the Corporation, or to any
other rights whatsoever except the rights expressed herein. No dividends are
payable or will accrue on this Warrant or the shares purchasable hereunder
until, and except to the extent that, this Warrant is exercised.

7.       EXCHANGE FOR OTHER DENOMINATIONS. This Warrant is exchangeable, on its
surrender by the registered owner to the Corporation, for new Warrants of like
tenor and date representing in the aggregate the right to purchase the number of
shares purchasable hereunder in denominations designated by the registered owner
at the time of surrender.

8.       TRANSFER. Except as otherwise provided, this Warrant is transferable
only on the books of the Corporation by the registered owner in person or by
attorney, on surrender of this Warrant, properly endorsed. However, because this
Warrant has not been registered under the Securities Act of 1933, as amended
(the "Securities Act"), and applicable state securities laws, this Warrant may
not be sold or transferred in the absence of an effective registration of it
under the Securities Act and all other applicable securities laws or an opinion
of counsel acceptable to the Corporation or its representatives that such sale
or transfer would not violate applicable securities laws or regulations. Any
Common Stock purchased upon exercise of this Warrant shall also be subject to
the same restrictions on transfer and will contain the same or similar transfer
legend found on the face of this Warrant.


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Class "AR" Warrant No.
                      ----
Page 3

9.       REGISTRATION RIGHTS. The terms of Section 6 of that certain Loan
Extension and Modification Agreement, dated as of March 29, 2002, by and among
the Corporation and the original holder hereof, are hereby incorporated by
reference as if set forth herein in full.

10.      RECOGNITION OF REGISTERED OWNER. Prior to due presentment for
registration of transfer of this Warrant, the Corporation may treat the
registered owner as the person exclusively entitled to receive notices and
otherwise to exercise rights hereunder.

11.      EFFECT OF STOCK SPLIT, ETC. If the Corporation, by stock dividend,
split, reverse split, reclassification of shares, or otherwise, changes as a
whole the outstanding Common Stock into a different number or class of shares,
then:

         (1)      the number and class of shares so changed shall, for the
purposes of this Warrant, replace the shares outstanding immediately prior to
the change; and

         (2)      the Warrant purchase price in effect, and the number of shares
purchasable under this Warrant, immediately prior to the date upon which the
change becomes effective, shall be proportionately adjusted (the price to the
nearest cent).

12.      EFFECT OF MERGER, ETC. If the Corporation consolidates with or merges
into another corporation, the registered owner shall thereafter be entitled on
exercise to purchase, with respect to each share of Common Stock purchasable
hereunder immediately before the consolidation or merger becomes effective, the
securities or other consideration to which a holder of one share of Common Stock
is entitled in the consolidation or merger to assure that all the provisions of
this Warrant shall thereafter be applicable, as nearly as reasonable may be, to
any securities or other consideration so deliverable on exercise of this
Warrant. The Corporation shall not consolidate or merge unless, prior to
consummation, the successor corporation (if other than the Corporation) assumes
the obligations of this Section 12 by written instrument executed and mailed to
the registered owner at the address of the owner on the books of the
Corporation. A sale or lease of all or substantially all the assets of the
Corporation for consideration (apart from the assumption of obligations)
consisting primarily of securities is a consolidation or merger for the
foregoing purposes.

13.      NOTICE OF ADJUSTMENT. On the happening of an event requiring an
adjustment of the Warrant purchase price or shares purchasable hereunder, the
Corporation shall forthwith give written notice to the registered owner stating
the adjusted Warrant purchase price and the adjusted number and kind of
securities or other property purchasable hereunder resulting from the event and
setting forth in reasonable detail the method of calculation and the facts upon
which the calculation is based. The board of directors of the Corporation,
acting in good faith, shall determine the calculation. Irrespective of any
adjustment or change in the Warrant purchase price or the number of shares
purchasable under this or any other Warrant of like tenor, the Warrants
theretofore and thereafter issued may continue to express the Warrant purchase
price per share and the number of shares purchasable as were expressed in the
Warrant when initially issued; provided, however, the Corporation may, in its
sole discretion, request the holder of this Warrant to exchange this Warrant for
a warrant of like tenor reflecting such adjustment or change provided for in
this Warrant, and the holder of this Warrant agrees to cooperate with the
Corporation to effect such exchange.

14.      NOTICE AND EFFECT OF DISSOLUTION, ETC. In case a voluntary or
involuntary dissolution, liquidation, or winding up of the Corporation (other
than in connection with a consolidation or merger


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Class "AR" Warrant No.
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Page 4

covered by Section 12 above) is at any time proposed, the Corporation shall give
at least 10 days written notice to the registered owner prior to the record date
as of which holders of Common Stock will be entitled to receive distributions as
a result of the proposed transaction. Such notice shall contain: (1) the date on
which the transaction is to take place; (2) the record date as of which holders
of Common Stock will be entitled to receive distributions as a result of the
transaction; (3) a brief description of the transaction; (4) a brief description
of the distributions to be made to holders of Common Stock as a result of the
transaction; and (5) an estimate of the fair value of the distributions. On the
date of the transaction, if it actually occurs, this Warrant and all rights
hereunder shall terminate.

15.      METHOD OF GIVING NOTICE; EXTENT REQUIRED. Notices shall be given by
first class mail, postage prepaid, addressed to the registered owner at the
address of the owner appearing in the records of the Corporation. No notice to
warrant holders is required except as specified in Sections 4, 9, 13 and 14.

16.      ACCESS TO INFORMATION. The Corporation will provide an opportunity to
any registered owner of this Warrant to ask questions of management of the
Corporation and to obtain information to the extent the Corporation has made
such information publicly available prior to any exercise of the owner's rights
to purchase Common Stock under this Warrant. Requests for information and any
other questions concerning the business and affairs of the Corporation should be
directed to the Vice President of Investor Relations of the Corporation at its
main offices.

                  [REMAINDER OF PAGE LEFT BLANK INTENTIONALLY]


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Class "AR" Warrant No.
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Page 5


         IN WITNESS WHEREOF, the Corporation has caused this Warrant to be
executed and delivered by is duly authorized officer as of the 1st day of May,
2002.

                           PROBEX CORP.

                           By: /s/  Bruce A. Hall
                               -------------------------------------------------
                           Name:    Bruce A. Hall
                           Title:   Senior Vice President


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Class "AR" Warrant No.
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Page 6

                                  TRANSFER FORM

         For value received, the undersigned hereby sells, assigns, and
transfers to

Name
     ------------------------------------------------------------------

Address
        ---------------------------------------------------------------

this Warrant and irrevocably appoints ___________________________ attorney (with
full power of substitution) to transfer this Warrant on the books of the
Corporation.

Date:

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

                                ------------------------------------------------
                                (Please sign exactly as name appears on Warrant)

                                Taxpayer ID No.
                                                -------------------------

In the presence of              Signature guaranteed by

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


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Class "AR" Warrant No.
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Page 7

                                  EXERCISE FORM

         The undersigned hereby: (1) irrevocably subscribes for
_________________ shares of your Common Stock pursuant to this Warrant, and
encloses payment of $____________ therefor; (2) requests that a certificate for
the shares be issued in the name of the undersigned and delivered to the
undersigned at the address below; and (3) if such number of shares is not all of
the shares purchasable hereunder, that a new Warrant of like tenor for the
balance of the remaining shares purchasable hereunder be issued in the name of
the undersigned and delivered to the undersigned at the address below.

Date:

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


                                -----------------------------------------------
                                (Please sign exactly as name appears on Warrant)

                                Address:
                                        ----------------------------------------

                                Taxpayer ID No.
                                               ---------------------------------