MUTUAL
RELEASE

    


    This
Mutual Release (the “Release”) is made and
entered into as of this __ day of November, 2010, by and among Penn Octane
Corporation (“POCC”), on the one
hand, and Rio Vista Energy Partners, L.P. (“RVEP”) and Rio Vista
GP, LLC, the general partner of RVEP (“RVGP” and together with RVEP, the “Rio Vista Parties”),
on the other hand.

     

    RECITALS

     

    A.          POCC
and RVEP are parties to that certain Securities Purchase and Sale Agreement with
Central Energy, LP (as successor by assignment to Central Energy, LLC) (“Buyer”) dated as of
May 25, 2010 and subsequently amended as of July 1, 2010, July 8, 2010, July 21,
2010 and November 17, 2010 (as amended, the “Purchase Agreement”)
pursuant to which, inter alia, (i) Buyer agreed to purchase certain Common Units
of RVEP from RVEP (the “Common Units”) and
all of the membership interests in RVGP (the “RVGP Units”) from
POCC and (ii) RVEP agreed to pay from the proceeds from such sale of Common
Units, $1.2 million to POCC (the “POCC Payment”) in
full satisfaction of all amounts owing to POCC as of the Closing (as defined in
the Purchase Agreement), including under that certain promissory note issued by
RVEP in favor of POCC dated as of [____________] (the “POCC
Note”).

     

    B.      
    Immediately prior to the Closing, POCC held 75% of the
RVGP Units and The Richter Living Trust (the “Richter Trust”) held
25% of the RVGP Units.  Pursuant to that certain Confidential
Settlement Agreement and General Release of Claims dated as of March 30, 2010 by
and among POCC, RVEP, Jerome B. Richter (“Richter”), Jerome B. Richter Capital
Resources, Inc. (“JBR”) and The Richter Trust (together with Richter and JBR,
the “JBR
Parties”), as modified by an Addendum thereto dated as of November 17,
2010, the Richter Trust agreed to transfer to POCC for no consideration, the
RVGP Units held by the Richter Trust upon receipt of payment by Richter of
$575,000 in full satisfaction of all amounts owing to the JBR Parties (the
“Richter Settlement
Payment”).

     

    C.           Pursuant
to the Purchase Agreement, at the Closing, (i) Buyer purchased Common Units from
RVEP, (ii) RVEP made the POCC Payment, (iii) POCC paid Richter the Richter
Settlement Payment, (iv) the Richter Trust transferred its RVGP Units to POCC,
and (iv) Buyer purchased from POCC all of the RVGP Units.

     

    D.          The
Rio Vista Parties desire to release POCC, and POCC desires to release the Rio
Vista Parties, from any and all liabilities and claims against the other arising
prior to the date hereof and through and including the date of this Release,
including without limitation, with respect to the POCC Note and any other
obligations (monetary or otherwise) owing by POCC or any Rio Vista Party to the
other (other than as set forth in the Purchase Agreement and related
documentation dated as of the date of this Release and contemplated thereby),
all on the terms and subject to the conditions contained herein.

     

    
      
         


      

      
         


        
          

        

      

      
         


      

    

     

    AGREEMENT

     

    In
consideration of the premises hereinabove and covenants hereinafter contained,
it is agreed by and between the parties hereto as follows:

     

    1.           Mutual
Release.  The Rio Vista Parties and each of its respective
officers, directors, employees, members, managers, representatives, agents,
affiliates, successors, assigns, family members and heirs (the “Rio Vista Releasing
Parties”), on the one hand, and POCC and its officers, directors,
employees, members, managers, representatives, agents, affiliates, successors,
assigns, family members and heirs (the “POCC Parties”), on
the other hand, each releases and absolutely discharges the other from any and
all claims, demands, damages, judgments, liens, losses, debts, liabilities,
accounts, reckonings, covenants, contracts, agreements, promises, sums of money,
obligations, attorneys' fees, costs, expenses, liens, actions, suits, dues, and
causes of action of every kind and nature, known or unknown, matured or
unmatured, absolute or contingent (the “Claims”), which any
of the Rio Vista Releasing Parties, on one hand, or any of the POCC Parties, on
the other hand, now have, have had at any time in the past, or may hereafter
have or acquire against the other for any reason or event occurring at any time
from the beginning of the world until the time of the execution of this Release
(other than in connection with the enforcement of the terms of this Release, the
Purchase Agreement and related agreements and instruments entered into in
connection therewith), including, without limitation, with respect to the POCC
Note.

     

    2.           No Rescission
Right.  Each of the parties hereto further agrees and
acknowledges that the facts in respect to which it has executed this Release and
which it now knows or believes to be true, may in fact be or may subsequently be
discovered by it to have been different from the facts now known or believed by
it to be true; and each party hereby accepts the risk and possibility that such
may be the case, and agrees that this Release shall not be subject to
rescission, cancellation, avoidance, or modification by reason of any difference
in facts.

     

    3.           Choice of
Law.  This Release shall be construed and interpreted under and
according to the laws of the State of New York.  In the event any
provisions of this Release are held by a court or tribunal of competent
jurisdiction to be unenforceable, the remaining provisions of this Release shall
remain in full force and effect; provided that the release by the Rio Vista
Releasing Parties shall not be enforceable if the release by the POCC Parties,
and vice
versa.

     

    4.           Assigns.  This
Release is and shall be binding upon and shall inure to the benefit of the
predecessors, successors, subsidiaries, affiliates, representatives, assigns,
directors, officers, attorneys or employees of each of the parties.

     

    5.           Entire
Agreement.  This Release constitutes the entire agreement
between the parties with regard to the subject matter hereof, there being no
oral, collateral, or supplemental agreement concerning the subject matter hereof
and supercedes all prior or contemporaneous agreements and understandings
pertaining thereto.  This Release may not be altered, amended,
modified or otherwise changed in any respect or particular, as to any party,
except by a writing duly executed by each party affected thereby.

     

    
      
         


      

      
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    6.           Representations of the
Parties.  Each of the parties hereto represents and warrants to
each other party hereto that: (i) he or it has not assigned to anyone any of the
rights, claims or causes of action that arose or could have arisen out of the
prior relationship between the POCC Parties and the Rio Vista Releasing Parties
including, without limitation, any of the rights, claims, or causes of action
arising under the POCC Note; and (ii) the execution of this Release has been
duly authorized by requisite corporate or partnership or limited liability
company actions, and that each of the persons executing this Release on behalf
of the respective parties hereto, is, likewise, duly authorized to do
so.

     

    7.           No Admission of Liability or
Fault.  Each party acknowledges and agrees that this Release
does not, in any manner, constitute an admission of liability or fault
whatsoever by any party and that this Release is made solely for the purpose of
settling any and all obligations owed or arising between the parties finally and
completely.

     

    8.           Counterparts;
Effectiveness.  This Release may be executed in multiple
counterparts, each of which shall be deemed an original, but all of which, when
taken together, shall constitute one and the same instrument.  A faxed
or PDF signature shall have the same force and effect as an original
signature.  This Release shall not be binding or enforceable until
executed and delivered by all parties hereto.

     

    [Signature
Page Follows]

     

    
      
         


      

      
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    IN WITNESS WHEREOF, this
Mutual Release is executed by the parties hereto as of the day and year first
above written.

     

    
      
        
          	 
      	
                  PENN
      OCTANE CORPORATION

                
	 
      	 
      	 
      
	 
      	
                  By:

                	
                  /s/ Ian T. Bothwell

                
	 
      	 
      	
                  Name:
      Ian T. Bothwell

                
	 
      	 
      	
                  Title:
      President

                
	 
      	 
      	 
      
	 
      	
                  RIO
      VISTA ENERGY PARTNER, L.P.

                
	 
      	 
      
	 
      	
                  By:
      Rio Vista GP, LLC, its General Partner

                
	 
      	 
      	 
      
	 
      	
                  By:

                	
                  /s/ Ian T. Bothwell

                
	 
      	 
      	
                  Name:
      Ian T. Bothwell

                
	 
      	 
      	
                  Title:
      President

                
	 
      	 
      	 
      
	 
      	
                  RIO
      VISTA GP, LLC

                
	 
      	 
      	 
      
	 
      	
                  By:

                	
                  /s/ Ian T. Bothwell

                
	 
      	 
      	
                  Name:
      Ian T. Bothwell

                
	 
      	 
      	
                  Title:
      President