AMENDMENT NO. 1


                                       TO


                                OMNIBUS AGREEMENT


                                     BETWEEN


                            PENN OCTANE CORPORATION,

                                RIO VISTA GP LLC,


                         RIO VISTA ENERGY PARTNERS L.P.


                                       AND


                      RIO VISTA OPERATING PARTNERSHIP L.P.


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                                 AMENDMENT NO. 1
                              TO OMNIBUS AGREEMENT

     THIS  AMENDMENT  NO.  1  TO OMNIBUS AGREEMENT (this "Agreement") is entered
                                                          ---------
into  effective as of September 16, 2004 by and among Penn Octane Corporation, a
Delaware  corporation  ("POCC"),  Rio Vista GP LLC, a Delaware limited liability
                         ----
company  (the  "General  Partner"),  Rio  Vista Energy Partners L.P., a Delaware
                ----------------
limited  partnership  (the  "Partnership"),  and Rio Vista Operating Partnership
                             -----------
L.P.  (the  "Operating  Partnership").  The  above-named  entities are sometimes
             ----------------------
referred  to  in  this  Agreement  each  as  a  "Party"  and collectively as the
                                                 -----
"Parties."
 -------

                                    RECITALS:

     WHEREAS,  each  of the Parties is a party to that certain Omnibus Agreement
dated  as  of  September  16,  2004  (the  "Original  Agreement");
                                            -------------------

     WHEREAS, it was and is the intent of the Parties under Section 2.2(b)(i) of
                                                             ---------------
the  Original Agreement that the Partnership indemnify, defend and hold harmless
the  POCC  Entities  from  and  against  any  Losses  arising  out  of events or
conditions  associated  with  the operation of the Assets rather than the Assets
and  the  Business  as  set  forth  in  the  Original  Agreement;

     WHEREAS,  it  was  and  is the intent of the Parties that the definition of
"Business"  in  the  Original Agreement means the business conducted through the
use  of  the  Assets;

     WHEREAS,  the  Parties  desire  to  amend the Original Agreement to reflect
their  intent  with  respect  to  such indemnity and definition of Business; and

     WHEREAS,  in  accordance  with  Section  4.7 of the Original Agreement, the
                                     ------------
amendment to the Original Agreement effected by this Agreement has been approved
by  the  Conflicts  Committee.

     NOW  THEREFORE,  in  consideration  of  the  premises  and  the  covenants,
conditions,  and  agreements  contained  herein, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
Parties  hereto  hereby  agree  as  follows:

     1. Capitalized terms used in this Agreement shall have the same meanings as
set  forth  in  the  Original  Agreement  unless  otherwise  defined  herein.

     2.  The  definition of "Business" in Article I of the Original Agreement is
                                          ---------
hereby  replaced,  amended,  restated  and  superseded  in its entirety with the
following:

          "Business" means the business conducted through the use of the Assets,
           --------
          including  (i) providing transportation, terminalling and distribution
          services  for hydrocarbon products and by-products, and (ii) marketing
          and  selling  hydrocarbon  products  and  by-products.

     3. Section 2.2(b)(i) of the Original Agreement is hereby replaced, amended,
        ------------------
estated  and  superseded  in  its  entirety  with  the  following:

     "(i)  the  operation  of  the  Assets,"


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     4.  Any  and  all of the terms and conditions of the Original Agreement are
hereby  amended  and  modified  wherever necessary, even though not specifically
addressed herein, so as to conform to the amendments and modifications contained
in  this  Agreement.

     5.  Except  as  modified  hereby,  all  of  the  provisions of the Original
Agreement are hereby ratified and confirmed and shall continue in full force and
effect.

     IN  WITNESS  WHEREOF, the parties hereto have executed this Amendment No. 1
to  Omnibus Agreement in multiple counterparts, each of which shall be deemed an
original,  as  of  the  date  and  year  first  above  written.

                                    RIO VISTA ENERGY PARTNERS, L.P.

                                    By: RIO VISTA GP LLC,
                                        On behalf of itself and on behalf of
                                        Partnership as its General Partner

                                        By: Richard Shore, Jr.
                                            -------------------------------
                                        Name: Richard Shore, Jr.
                                        Title: President


                                    RIO VISTA OPERATING PARTNERSHIP L.P.

                                    By: RIO VISTA OPERATING GP LLC

                                    By: RIO VISTA ENERGY PARTNERS
                                    L.P., its sole member

                                        By: RIO VISTA GP LLC

                                        By: Richard Shore, Jr.
                                           -------------------------------
                                            Richard Shore, Jr.,
                                            President

                                    PENN  OCTANE  CORPORATION


                                    By: Jerome  B.  Richter
                                        -------------------
                                    Name: Jerome B. Richter
                                    Title: Chief Executive Officer


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