RELEASE

     

    This
RELEASE is made and entered into as of the 17th day of November, 2010 by Rio
Vista Energy Partners, L.P., a Delaware limited partnership (“RVEP”), Rio Vista GP, LLC, a
Delaware limited liability company and the general partner of RVEP (“RVGP”) and Central Energy, LP,
a Delaware limited partnership (“Buyer”, and together with RVEP
and RVGP, the “Releasors”), and the persons
identified on Schedule I attached hereto (collectively, the “Releasees”).

     

    WHEREAS,
RVEP is party to that certain Purchase and Sale Agreement dated as of May 25,
2010, as modified by amendments thereto dated as of July 1, 2010, July 8, 2010,
July 21, 2010, October __, 2010, November 12, 2010 and November 17, 2010,
respectively (as amended, the “Purchase Agreement”), by and
among Buyer, RVEP and Penn Octane Corporation, a Delaware corporation (“POCC”), pursuant to which,
among other things, (i) RVEP will sell and issue to the Buyer 12,724,019 Common
Units (as defined in the Partnership Agreement) and (ii) POCC will sell to the
Buyer all of their respective membership interests in the General Partner (the
“Sale of the GP
Interests”); and

    


    WHEREAS,
Section 7.7 of the First Amended and Restated Agreement of Limited Partnership
of RVEP, dated as of September 16, 2004 (as amended, the “Partnership Agreement”)
contains certain indemnities and releases in favor of Indemnitees (as defined in
the Partnership Agreement), including without limitation the
Releasees;

     

    WHEREAS,
as a condition to the closing of the transactions contemplated by the Purchase
Agreement, the Parties desire to confirm the provisions of Section 7.7 as they
apply to the Releasees and expressly release the Releasees from any claims that
may arise out of their service to RVEP and RVGP as members of RVGP’s Board of
Managers or as officers of either such Party and their actions in such
capacities taken prior to the Closing (as defined in the Purchase
Agreement).

     

    NOW,
THEREFORE, in consideration of the premises set forth hereinabove and other
consideration the receipt and sufficiency of which is hereby acknowledged, the
parties hereto agree as follows:

     

    Each of
the Releasors hereby releases and forever discharges each of the Releasees and
their respective agents, attorneys and assigns from any and all claims, rights,
demands, liabilities, actions or causes of action, obligations, and damages of
any kind, name, nature or description, either at law or in equity, whether known
or unknown, whether past or future, that in any manner may have arisen out of
actions taken by such Releasee prior to the Closing (collectively, “Claims”); provided however
such releases shall not extend to any Claims for which a Releasee would not be
entitled to indemnification pursuant to Section 7.7 of the Partnership Agreement
as in effect as of the date of this release unless such Claim has been
previously disclosed as part of RVEP’s filings with the Securities Exchange
Commission or in an Exhibit or a Schedule to the Purchase
Agreement.

     

    Each of
the Releasors agrees not to amend Section 7.7 of the Partnership Agreement as it
applies to the Releasees without the prior written consent of the affected
Releasees.

     

    
      
         


      

      
         


        
          

        

      

      
         


      

    

     

    (b)           The
preceding release extends to and includes any and all claims, liabilities,
injuries, damages, and causes of action against the Releasees that any Releasor
does not presently anticipate, know, or suspect to exist, but that may develop,
accrue, or be discovered in the future.

    


    EACH
INSIDER EXPRESSLY WAIVES ALL RIGHTS UNDER CALIFORNIA CIVIL CODE SECTION 1542 AND
ANY SIMILAR APPLICABLE STATE OR FEDERAL STATUTE, WHICH PROVIDES: “A general
release does not extend to claims which the creditor does not know or suspect to
exist in his favor at the time of executing the release, which if known by him
must have materially affected his settlement with the debtor.”

    


    (c)           Each
Releasor represents and warrants that it has considered the possibility that
claims, liabilities, injuries, damages and causes of action against the
Releasees that it does not presently know or suspect to exist in its favor may
develop, accrue, or be discovered in the future, and that it voluntarily assumes
that risk as part of the consideration for this Release.

    


    This Release may be executed in two or
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same Release.  This Release may
also be executed and delivered by facsimile, email or other electronic signature
and in two or more counterparts, each of which shall be deemed an original, but
all of which together shall constitute one and the same instrument.

     

    This Release and the legal relations
among the parties shall be governed by, and construed and enforced in accordance
with, the laws of the State of Delaware, without regard to its conflict of laws
rules.

     

    [SIGNATURE
PAGE FOLLOWS]


    
      
         


      

      
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    IN
WITNESS WHEREOF, the parties hereto have executed this Release on and as of the
day and year first above written.

     

    
      
        
          
            	
                    RIO
      VISTA ENERGY PARTNERS, L.P.

                  
	 
      	 
      
	
                    By:

                  	
                    /s/ Ian T. Bothwell

                  
	
                    Name: 
       Ian T. Bothwell

                  
	
                    Title:
      President of Rio Vista GP, LLC, its

                    General
      Partner

                  
	 
      	 
      
	
                    RIO
      VISTA GP, LLC

                  
	 
      	 
      
	
                    By:

                  	
                    /s/ Ian T. Bothwell

                  
	
                    Name: 
        Ian T. Bothwell

                  
	
                    Title:
      President

                  
	 
      	 
      
	
                    CENTRAL
      ENERGY, L.P.

                  
	 
      
	
                    By:
      Central Energy, LLC

                  
	
                    Its:
      General Partner

                  
	 
      	 
      
	
                    By:

                  	
                    /s/ Imad Anbouba

                  
	
                    Name: 
       Imad Anbouba

                  
	
                    Title:    
      Managing Member

                  
	 
      	 
      
	
                    By:

                  	
                    /s/ Carter R. Montgomery

                  
	
                    Name:  Carter
      R. Montgomery

                  
	
                    Title:   
      Managing Member

                  


          

        

      

    

    


    [Signature
Page toRelease]


    
      
         


      

      
         


        
          

        

      

      
         


      

    


    SCHEDULE
I

    To

    Release

    


    Releasees

    


    Ian
T  Bothwell

    


    Bruce I.
Raben

    


    Ricardo
Rodriguez

    


    Murray J.
Feiwell

    


    Nicholas
J. Singer

    


    Douglas
G. Manner


    
      
         


      

      
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