EXHIBIT 10.3

                     FIRST AMENDMENT TO PURCHASE AGREEMENT
                     -------------------------------------

         This FIRST AMENDMENT TO PURCHASE AGREEMENT (the "Amendment") is entered
into as of September 30, 1996, by and between MOTORVAC TECHNOLOGIES, INC., a 
Delaware corporation ("MotorVac"), on the one hand, and INTERNATIONAL TURBO 
CENTER, INC., a California corporation ("ITC"), and ENVIROMOTIVE, INC., a 
California corporation and a wholly-owned subsidiary of ITC ("Enviromotive," 
and, collectively with ITC, the "Companies"), on the other hand.

                                   RECITALS:
                                   --------

         A. MotorVac and the Companies have previously entered into a Purchase 
Agreement entered into as of February 22, 1996, but made effective as of 
December 31, 1995 (the "Purchase Agreement").

         B. MotorVac and the Companies desire to amend the Purchase Agreement to
provide that the Companies shall accept aggregate payments of (i) One Hundred
Seventy-Two Thousand Fifty-Nine and 21/100 Dollars ($172,059.21) in full payment
of the Diesel Detergent Payments (as defined in the Purchase Agreement) and (ii)
Twenty-Eight Thousand Dollars ($28,000) in full payment of the Additional
Payments (as defined in the Purchase Agreement).

                                  AGREEMENT:
                                  ---------
         NOW, THEREFORE, in consideration of the foregoing Recitals and the 
mutual agreements and obligations of the parties hereto, and for other good and 
valuable consideration, the receipt and sufficiency of which is hereby 
acknowledged, the parties hereto agree as follows:

         1. Amendment. The Companies hereby agree that payment by MotorVac in
            ---------  
the amount of (i) One Hundred Seventy-Two Thousand Fifty-Nine and 21/100 Dollars
($172,059.21) shall be accepted by the Companies as payment in full of all
Diesel Detergent Payments (as defined in the Purchase Agreement) payable under
the Purchase Agreement (the "Accelerated Diesel Payment") and (ii) Twenty-Eight
Thousand Dollars ($28,000) shall be accepted by the Companies as payment in full
of the Additional Payments (as defined in the Purchase Agreement) payable
under the Purchase Agreement (the "Accelerated Additional Payment"). MotorVac
shall pay the Accelerated Diesel Payment to the Guarantors (as defined below)
and shall deliver the Accelerated Additional Payment to Allen, Matkins, Leck,
Gamble & Mallory LLP for delivery to the Internal Revenue Service, in each case
on behalf of the Companies, within ten (10) days of receipt of a fully executed
copy of this Amendment executed by Enviromotive and ITC and an executed
acknowledgment from each of the Guarantors in a form reasonably acceptable to
MotorVac (the "Payment Date"). In consideration of MotorVac


 
agreeing to make the Accelerated Diesel Payment and the Accelerated Additional 
Payment, the Companies agree that MotorVac shall be fully released and 
discharged from any further obligation to make any Diesel Detergent Payments 
and/or Additional Payments under Sections 1(a)(ii) and (iii) of the Purchase 
Agreement or otherwise under the Purchase Agreement.

          2.   Payment to Guarantors.  By letter dated May 23, 1996 (the 
               ---------------------
"Guarantor Instruction Letter"), Enviromotive instructed MotorVac to make all 
payments of the Diesel Detergent Payments to certain individuals (collectively, 
the "Guarantors") in the amounts set forth in the Guarantor Instruction Letter.
Enviromotive hereby notifies and instructs MotorVac to pay on behalf of
Enviromotive directly to the Guarantors (or their designee) and in proportion to
the percentages listed in the Guarantor Instruction Letter, the full amount of
the Accelerated Diesel Payment. Enviromotive acknowledges and agrees that the
receipt by the Guarantors of the Accelerated Diesel Payment shall be deemed to
be payment in full of the Diesel Detergent Payments and the Accelerated Diesel
Payment to Enviromotive. Enviromotive acknowledges that MotorVac's agreement to
make the Accelerated Diesel Payment is conditioned upon each of the Guarantors
agreeing to receive its portion of the Accelerated Diesel Payment and executing
and delivering to MotorVac an acknowledgment, reasonably acceptable to MotorVac,
of the terms of this Amendment.

          3.   Payment to Internal Revenue Service.  The Companies hereby 
               -----------------------------------
instruct MotorVac to pay the Accelerated Additional Payment to the Internal 
Revenue Service for the benefit of ITC Trust Fund Account No. 95-2458416.  Not 
later than the Payment Date, MotorVac shall deliver to Allen, Matkins, Leck, 
Gamble & Mallory LLP, MotorVac's attorneys, a check in the amount of 
Twenty-Eight Thousand Dollars ($28,000) representing the Accelerated Additional 
Payment.  MotorVac shall instruct Allen, Matkins, Leck, Gamble & Mallory LLP to 
deliver such amount to the Internal Revenue Service, Department of the Treasury,
1130 Civic Center Boulevard, Suite B, Yuba City, California 95933 Attention:  
Barbara Lane, together with a copy of the check to Ray Mushet, Jack Meismer and 
Doug Decinces.  The check representing payment of the Accelerated Additional 
Payment shall note that it is in payment of the Trust Fund Account balance, 
Account No. 95-2458416, for the benefit of ITC.

          4.   Miscellaneous.  Except as amended hereby, the Purchase Agreement 
               -------------
shall remain in full force and effect.  This Amendment shall be governed by and 
construed in accordance with the laws of the State of California and may be 
amended only by a written instrument executed by each of the parties hereto.  
This Amendment may be executed in one or more counterparts (including by means 
of a telecopied signature page), each of which shall be deemed an original, but
all of which together shall constitute a single agreement.  This Amendment, 
together with the Purchase Agreement (as amended hereby) and the Guarantor 
Instruction Letter (as amended hereby), constitutes the entire agreement and 
understanding between the parties hereto with respect to the subject matter 
hereof, is intended as a complete and exclusive statement of the terms of their 
agreement and supersedes any prior or contemporaneous oral or written agreements
or understandings related to the subject matter hereof.

          IN WITNESS HEREOF, the parties hereto have executed this Amendment as 
of the date first above written.

                                      -2-

 
         "Enviromotive"          ENVIROMOTIVE, INC., a California corporation

                                 By:         /s/ Jack Misemer                 
                                     _________________________________________

                                      Name:      Jack Misemer                 
                                            __________________________________

                                      Title:     President                    
                                             _________________________________


         "ITC"                   INTERNATIONAL TURBO CENTER, INC., a
                                 California corporation

                                 By:         /s/ Jack Misemer                 
                                     _________________________________________

                                      Name:      Jack Misemer                 
                                            __________________________________

                                      Title:     President                    
                                             _________________________________

         "MotorVac"              MOTORVAC TECHNOLOGIES, INC., a 
                                 Delaware corporation

                                 By:  /s/ Allan T. Maguire                    
                                     _________________________________________
                                      Allan T. Maguire
                                      Vice President, Finance and Chief 
                                      Financial Officer

                                      -3-