EXHIBIT 4.3.27


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

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

                        PURCHASE PRICE PER SHARE: $1.243

EXPIRATION DATE: 5:00 p.m., Dallas, Texas Time, On September 1, 2006


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

<PAGE>

Class "AK-A" Warrant No. ____
Page 2


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,
the Corporation shall either (1) pay therefor cash equal to the same fraction of
the then current Warrant  purchase price per share or, at its option,  (2) issue
scrip for the  fraction,  in  registered or bearer form approved by the board of
directors  of the  Corporation,  which  shall  entitle  the  holder to receive a
certificate for a full share of Common Stock on surrender of scrip aggregating a
full share.  Scrip may become void after a reasonable  period (but not less than
six months after the expiration date of this Warrant) determined by the board of
directors  and  specified in the scrip.  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 on or prior to  January  1,  2004,  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  which 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 $1.243 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 the 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 such
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 the 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.

<PAGE>
Class "AK-A" Warrant No. ____
Page 3


9.       Registration Rights.

         (1) Each time that the Corporation  proposes for any reason to register
any of its Common Stock under the Securities Act in connection with the proposed
offer and sale of its Common  Stock for money  either for its own  account or on
behalf  of any other  security  holder  ("Proposed  Registration"),  other  than
pursuant to a registration  statement on Form S-4, S-8 or any successor thereto,
the Corporation shall promptly give written notice of such Proposed Registration
to the holder  hereof and shall  offer such  holder  hereof the right to request
inclusion of the shares  issued or issuable upon the exercise of this Warrant in
the Proposed Registration.

         (2) The holder hereof shall have ten (10) days from the receipt of such
notice to deliver to the Corporation a written request  specifying the number of
shares such holder hereof  intends to sell and the holder's  intended  method of
disposition.

         (3) In the event that the Proposed  Registration by the Corporation is,
in whole or in part, an underwritten  public offering,  the Corporation shall so
advise the holder hereof as part of the written notice given pursuant to Section
9(1),  and any request under Section 9(2) must specify that the shares of Common
Stock be included in the  underwriting  on the same terms and  conditions as the
shares of Common Stock, if any, otherwise being sold through  underwriters under
such registration.

         (4) Upon receipt of a written  request  pursuant to Section  9(2),  the
Corporation shall promptly use its commercially  reasonable efforts to cause all
such shares of Common Stock held by the holder hereof to be registered under the
Securities Act (and included in any related  qualifications  under blue sky laws
or other  compliance),  to the extent required to permit the sale or disposition
as set forth in the Proposed Registration.

         (5) In the event that the offering is to be an  underwritten  offering,
the holder  hereof  proposing to  distribute  its shares of Common Stock through
such underwritten  offering agrees to enter into an underwriting  agreement with
the  underwriter  or  underwriters   selected  for  such   underwriting  by  the
Corporation.

         (6) Notwithstanding the foregoing,  if in its good faith judgment,  the
managing underwriter determines and advises in writing that the inclusion of all
shares of Common Stock issued or issuable with respect to this Warrant  proposed
to be included in the  underwritten  public  offering,  together  with any other
issued and outstanding shares of Common Stock proposed to be included therein by
holders  other than the  holder  hereof,  would  interfere  with the  successful
marketing of such  securities,  then the number of such shares to be included in
such underwritten  public offering shall be reduced, on a pro-rata basis (except
only those shares held by holders  that have the benefit of any priority  rights
previously  granted such holders),  based upon the number of shares held by each
holder,  including the holder hereof; provided that, in connection with any such
public  offering,  if the  managing  underwriter  reasonably  and in good  faith
recommends,  which recommendation and supporting reasoning shall be delivered in
writing to the holders,  that no amount of shares,  including shares held by the
holder hereof, should be included in the underwritten public offering,  then the
Corporation  shall not be  required  to include  any such  shares in such public
offering.

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.

<PAGE>
Class "AK-A" Warrant No. ____
Page 4


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 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.

<PAGE>
Class "AK-A" Warrant No. ____
Page 5


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]

<PAGE>
Class "AK-A" Warrant No. ____
Page 6


         IN WITNESS  WHEREOF,  the  Corporation  has caused  this  Warrant to be
executed  and  delivered  by its duly  authorized  officer  as of the 1st day of
September, 2001.



                                    PROBEX CORP.



                                    By: ________________________________
                                    Name:    Bruce A. Hall
                                    Title:   Senior Vice President & Chief
                                             Financial Officer



<PAGE>
Class "AK-A" Warrant No. ____
Page 7


                                  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:

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

                                Taxpayer ID No. ________________________

In the presence of              Signature guaranteed by

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



<PAGE>
Class "AK-A" Warrant No. ____
Page 8


                                  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:

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

                                Address:_________________________________
                                        _________________________________


                                Taxpayer ID No.___________________________