**Exhibit 10.43****REAFFIRMATION OF SECURITY AGREEMENTS**This REAFFIRMATION OF SECURITY AGREEMENTS, dated as of July 26, 2007 (this “SecurityReaffirmation Agreement”), is by and among Rio Vista Energy Partners L.P., a Delaware limitedpartnership (the “Borrower” and a “Grantor”), Penn Octane Corporation, a Delaware corporation(“POC” and a “Grantor”) and Rio Vista Operating Partnership L.P., a Delaware limited partnership(“RVOP”, a “Grantor” and together with the Borrower and POC, the “Grantors”) and RZB Finance LLC(the “Lender”).RECITALSWHEREAS, the Borrower has entered into a Loan Agreement dated as of July 26, 2007 (as amended,supplemented or otherwise modified from time to time, the “Loan Agreement”; capitalized terms usedherein and not otherwise defined herein shall have the meanings given to them in the LoanAgreement) between the Borrower and the Lender;WHEREAS, as a condition precedent to the effectiveness of the Loan Agreement, each of POC andRVOP has executed and delivered to the Lender a Guaranty and Agreement dated as of July 26, 2007(as each may be amended, supplemented or otherwise modified from time to time, each individually, a“Guarantee” and collectively, the “Guarantees”);WHEREAS, the Borrower, POC and RVOP have heretofore executed and delivered to the LenderGeneral Security Agreements dated September 15, 2004, February 13, 2002 and September 15, 2004,respectively (as they may be amended, supplemented or otherwise modified from time to time, eachindividually, a “Security Agreement” and collectively, the “Security Agreements”); andWHEREAS, the Grantors wish to reaffirm that the provisions of the Security Agreements shallremain in full force and effect and to confirm that the liens granted thereunder secure (i) in thecase of the Borrower’s Security Agreement, the Obligations, (ii) in the case of POC’s SecurityAgreement, the obligations of POC under its Guarantee and (iii) in the case of RVOP’s SecurityAgreement, the obligations of RVOP under its Guarantee.NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency of which arehereby acknowledged, the parties hereto hereby agree as follows:1. The Borrower hereby (i) reaffirms its Security Agreement and all of its obligationsthereunder, (ii) certifies that the Liens granted thereunder are continuing and in full force andeffect, and (iii) confirms that the Liens granted thereunder secure the Obligations in addition toall other Obligations (as defined in the Borrower’s Security Agreement).
 
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2. POC hereby (i) reaffirms its Security Agreement and all of its obligations thereunder, (ii)certifies that the Liens granted thereunder are continuing and in full force and effect, and (iii)confirms that the Liens granted thereunder secure its obligations under its Guarantee in additionto all other Obligations (as defined in POC’s Security Agreement).3. RVOP hereby (i) reaffirms its Security Agreement and all of its obligations thereunder,(ii) certifies that the Liens granted thereunder are continuing and in full force and effect, and(iii) confirms that the Liens granted thereunder secure its obligations under its Guarantee inaddition to all other Obligations (as defined in RVOP’s Security Agreement).4. Each of the Grantors acknowledges that this Security Reaffirmation Agreement is a LoanDocument.5. This Security Reaffirmation Agreement shall be binding upon and inure to the benefit of theparties hereto and their respective successors and assigns.6. THIS SECURITY REAFFIRMATION AGREEMENT SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED ANDENFORCED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TOCONFLICTS OF LAWS PRINCIPLES**.**7. This Security Reaffirmation Agreement and any amendments, waivers, consents, or supplementsmay be executed in any number of counterparts and by different parties hereto in separatecounterparts, each of which when so executed and delivered shall be deemed an original, but all ofwhich counterparts together shall constitute but one and the same instrument. This SecurityReaffirmation Agreement shall become effective upon the execution of a counterpart hereof by eachof the parties hereto. Delivery of an executed counterpart of a signature page to this SecurityReaffirmation Agreement by telecopier shall be as effective as delivery of a manually executedcounterpart thereof.
 
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IN WITNESS WHEREOF, the parties have caused this Security Reaffirmation Agreement to be dulyexecuted and delivered the day and year first above written.      GRANTORS