Rio Vista Energy Partners L.P. (NASDAQ: RVEP), an energy services master limited partnership, announced today that effective opening of business on Thursday, December 17, 2009, Rio Vista’s common units will commence trading in the “Pink Sheets” and Rio Vista intends to sponsor Real-Time Level 2 Quotes. On December 15, 2009, Rio Vista received a letter from the Nasdaq Stock Market (Nasdaq) staff indicating that the Listing Qualifications Panel (the “Hearing Panel”) determined to deny Rio Vista’s request for continued listing and would suspend trading of Rio Vista’s common units effective the opening of business on December 17, 2009. Rio Vista will still be required to file all required reports with the Securities and Exchange Commission.

About Rio Vista Energy Partners L.P.

Rio Vista is a master limited partnership engaged in liquid bulk storage, transloading and transportation of chemicals and petroleum products through its assets and operations in Hopewell, Virginia. Penn Octane Corporation (OTCBB: POCC) owns 75% of Rio Vista GP LLC, the general partner of Rio Vista.

Forward-Looking Statements

Certain of the statements in this news release are forward-looking statements, including statements regarding the delisting of Rio Vista’s common units from Nasdaq and the subsequent trading in the “Pink Sheets”. Upon the delisting of Rio Vista’s common units from Nasdaq, common unitholders may be negatively impacted. Additional information regarding risks affecting Rio Vista’s business may be found in Rio Vista’s most recent reports on Form 8-K, Form 10-Q and Form 10-K filed with the Securities and Exchange Commission.