**Exhibit 10.28****CONSULTANT AGREEMENT**This Agreement is made and entered into as of the 2nd day of July, 2007 between Rio Vista EnergyPartners, L.P. (the “Company”) and CEOcast, Inc. (the “Consultant”)In consideration of and for the mutual promises and covenants contained herein, and for other goodand valuable consideration, the receipt of which is hereby acknowledged, the parties agree asfollows:1. Purpose. The Company hereby employs the Consultant during the Term (as defined below)torender Investor Relations services to the Company, upon the terms and conditions as set forthherein. 2. Term. This Agreement shall be effective for a one-year period (the “Term”) commencingonthe date hereof.   Thereafter, unless terminated by either party by providing written notice to the other party onor before May 30, 2008, this Agreement shall automatically renew for additional one yearperiods (“Additional Period”) under the same terms and conditions except that either party mayterminate the Agreement at any time during any Additional Period by providing 60 days writtennotice to the other party. If this Agreement is terminated, then any cash and/or unit paymentsshall be made on a prorata basis in accordance with the same payment schedule provided for inthe original term. In determining the amount of units to be granted in Additional Periods, theparties agree that the amount will be calculated as follows: The first $15,000 of value (orprorata portion thereof) based on the closing price of Common Units as of the Additional Periodanniversary date, the next $25,000 of value (or prorata portion thereof) based on average ofthe closing price of the Common Units during the thirty calendar days immediately preceding theSeptember 30 quarter during the Additional Period, the next $25,000 of value (or prorataportion thereof) based on average of the closing price of the Common Units during the thirtycalendar days immediately preceding the December 31 quarter during the Additional Period, andthe next $25,000 of value (or prorata portion thereof) based on average of the closing price ofthe Common Units during the thirty calendar days immediately preceding the March 31 quarterduring the Additional Period. Any Common Units due to Consultant under any Additional periodshall be made at the soonest practical date after March 31 of the annual period in which theAdditional period falls, at the best efforts of the Company. 3. Duties of Consultant. During the term of this Agreement, the Consultant shallprovide to theCompany those services outlined in Exhibit A. Notwithstanding the foregoing, it isunderstood and acknowledged by the parties that the Consultant: (a) shall perform its analysisand reach its conclusions about the Company independently, and that the Company shall haveno involvement therein; and (b) shall not render advice and/or services to the Company in anymanner, directly or indirectly, that is in connection with the offer or sale of securities in acapital raising transaction or that could result in market making. 4. Expenses. The Company, upon receipt of appropriate supporting documentation, shallreimburse the Consultant for any and all reasonable out-of-pocket expenses incurred by it inconnection with services requested by the Company, including, but not limited to, all chargesfor travel, printing costs and other expenses spent on the Company’s behalf. The Companyshall immediately pay such expenses upon the presentation of invoices. Consultant shall notincur more than $500 in expenses without the express written consent of the Company.
 
1

 
5. Compensation. For services to be rendered by the Consultant hereunder, theConsultant shallreceive from the Company upon the signing of the Agreement: (a) $15,000 (the “Retainer),which shall represent the first and last month’s payment under the Agreement and (b) theCompany shall pay Consultant $7,500 per month on or before the 2nd day of each of the nextten months excluding the final month of the Agreement.   The Company shall also issue Consultant (a) 1,399 of the Company’s fully-paid, non-assessablecommon units (“Common Units”) and (b) $75,000 worth of Common units on March 31, 2008 based onthe following calculation of units; $25,000 divided by the average of the closing price of theCommon Units during the thirty calendar days immediately preceding September 30, 2007, $25,000divided by the average of the closing price of the Common Units during the thirty calendardays immediately preceding December 31, 2007 and $25,000 divided by the average of the closingprice of the Common Units during the thirty calendar days immediately preceding March 31,2008. Company shall grant Consultant or its designee “piggyback” registration rights, whichshall entitle Consultant or its designee to register its Common Stock in connection with theCompany’s next registration of securities on Form S-3, at Company’s expense, subject tounderwriter cutback and customary indemnification covenants. Company shall also agree toprovide, at Company’s expense, a legal opinion which will allow Consultant or its designee tosell its Common Units under Rule 144. The delivery of any Common Units provided for hereinshall be made at the soonest practical date after March 31, 2008, based on the best efforts ofthe Company. Company shall also pay Consultant Expenses as outlined in Section 4 promptly. 6. Voting Agreements. Because of the nature of the services being provided byConsultanthereunder, Consultant acknowledges that if it may receive access to Confidential Information(as defined in Section 7 hereof) and that, as a consultant to the Company, it will attempt toprovide advice that serves the best interest of the Company. Because of the uniqueness of thisrelationship, the Consultant covenants and agrees that, with respect to the Common Units thatit receives. Consultant shall, at all times that it is the beneficial owner of such units, votesuchunits on all matters coming before it as a unitholder of the Company in the same manner asthe majority of the Board of Managers of the Company shall recommend. 7. Confidentiality. Consultant acknowledges that as a consequence of its relationshipwith theCompany, it may be given access to confidential information which may include thefollowing types of information: financial statements and related financial information withrespect to the Company and its subsidiaries, information regarding pending transactions andSEC filings, trade secrets, products, product development, product packaging,future marketing materials, business plans, certain methods of operations,procedures,improvements, systems, customer lists, supplier lists and specifications, and other private andconfidential materials concerning the Company’s business (collectively, “ConfidentialInformation”).   Consultant covenants and agrees to hold such Confidential Information strictly confidential andshall only use such information solely to perform its duties under this Agreement, andConsultant shall refrain from allowing such information to be used in any way for its ownprivate or commercial purposes. Consultant shall also refrain from disclosing any suchConfidential Information to any third parties. Consultant agrees to take all reasonableprecautions to prevent any trading in securities of Company or Perm Octane Corporation byConsultant’s officers, directors, employees and agents who have access to such ConfidentialInformation. Consultant further agrees that upon termination or expiration of this Agreement,it will return all Confidential Information and copies thereof to the Company and will destroyall notes, reports and other material prepared by or for it containing ConfidentialInformation. Consultant understands and agrees that the Company might be irreparably harmed byviolation of this Agreement and that monetary damages may be inadequate to compensate theCompany. Accordingly, the Consultant agrees that, in addition to any other remediesavailable to it at law or in equity, the Company shall be entitled to injunctive relief toenforce the terms of this Agreement.
 
2

 
  Notwithstanding the foregoing, nothing herein shall be construed as prohibiting Consultantfrom disclosing any Confidential Information (a) which at the time of disclosure. Consultantcan demonstrate either was in the public domain and generally available to the public orthereafter becomes a part of the public domain and is generally available to the public bypublication or otherwise through no act or omission of the Consultant; (b) which Consultantcan establish was independently developed by a third party who developed it without the use ofthe Confidential Information and who did not acquire it directly or indirectly from Consultantunder an obligation of confidence; (c) which Consultant can show was received by it after thetermination of this Agreement from a third party who did not acquire it directly or indirectlyfrom the Company under an obligation of confidence; or (d) to the extent that the Consultantcan reasonably demonstrate such disclosure is required by law or in any legal proceeding,governmental investigation, or other similar proceeding after giving reasonable notice toCompany in order to permit Company to seek an appropriate protective order before suchdisclosure. 8. Governing Law; Venue; Jurisdiction. This Agreement shall be construed and enforcedin accordance with and governed by the laws of the State of New York, without reference toprinciples of conflicts or choice of law thereof. Each of the parties consents to thejurisdiction of the U.S. District Court in the Southern District of New York in connectionwith any dispute arising under this Agreement and hereby waives, to the maximum extentpermitted by law, any objection, including any objection based on forumnonconveniens. to the bringing of any such proceeding in such jurisdictions. Each partyhereby agrees that if another party to this Agreement obtains a final, non-appealablejudgment against it in such a proceeding, the party which obtained such judgment may enforcesame by summary procedure in the courts of any country having jurisdiction over the partyagainst whom such judgment was obtained, and each party hereby waives any defenses availableto it under local law and agrees to the enforcement of such a judgment. Each party to thisAgreement irrevocably consents to the service of process in any such proceeding by themailing of copies thereof by registered or certified mail, postage prepaid, to such party atit address set forth herein. Nothing herein shall affect the right of any party to serveprocess in any other manner permitted by law. Each party waives its right to a trial by jury. 9. Miscellaneous.(a) Any notice or other communication between parties hereto shall be sufficiently given ifsent by certified or registered mail, postage prepaid, if to the Company, addressed to itatRio Vista Energy Partners L.P., 840 Apollo Street, Suite 313, El Segundo, CA 90245Attention: Chief Financial Officer, facsimile number (310) 563-6255, or if to Consultant,addressed to it at CEOcast, Inc., 369 Lexington Avenue – 4th Floor, New York,NY10017 Attention: Administrator, facsimile number: (212)732-1131, or to such address asmay hereafter be designated in writing by one party to the other. Any notice or othercommunication hereunder shall be deemed given three business days after deposit in themail if mailed by certified mail, return receipt requested, or on the business day afterdeposit with an overnight courier service for next day delivery, or on the date deliveredby hand or by facsimile with accurate confirmation generated by the transmittingfacsimile machine, at the address or number designated above (if delivered on abusinessday during normal business hours where such notice is to be received), or the firstbusiness day following such delivery (if delivered other than on a business day duringnormal business hours where such notice is to be received).
 
3

 
(b) This Agreement embodies the entire Agreement and understanding between theCompany and the Consultant and supersedes any and all negotiations, prior discussionsand preliminary and prior arrangements and understandings related to the central subjectmatter hereof. (c) This Agreement has been duly authorized, executed and delivered by and on behalf of theCompany and the Consultant. (d) This Agreement and all rights, liabilities and obligations hereunder shall be binding uponand inure to the benefit of each party’s successors but may not be assigned without theprior written approval of the other party.   IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the datehereof.       RIO VISTA ENERGY PARTNERS, L.P.       By: Rio Vista GP LLC       By:              CEOCAST, INC.       By:       
 
4

 
**EXHIBIT A**1. Non-deal road shows including meetings with brokers, fund managers and high net-worth investors.2. Company featured on the Home Page of CEOcast site for one week.3. The writing and/or review and/or distribution of all Company press releases (includingPenn Octane Corporation) to major new wire services as well as to over 275,000 opt-inenergy investors.4. Company covered in CEOcast newsletter.5. Calls to 200 brokers on each news release.6. Interviews on ceocast.com web site as desired with distribution to over 275,000 opt-inenergy investors.7. Investor line to handle call volume.8. Strategic advice, including technical analysis to ensure that press release distributionand other dissemination of news releases generates the maximum impact.9. Maintenance of company databases.
 
5