Rio Vista To Make Quarterly Distribution of $0.25 Per Unit on August 14, 2008

Business Wire, August 1, 2008

BROWNSVILLE, Texas -- Rio Vista Energy Partners L.P. (NASDAQ:RVEP), an energy services master limited partnership, announced today that it has scheduled a cash distribution to its common unit holders. The distribution, covering the second quarter ended June 30, 2008, is expected to be in an amount equal to $0.25 per common unit. The distribution is scheduled to be paid on August 14, 2008 to all holders of record of Rio Vista common units as of the close of business on August 11, 2008.

About Rio Vista Energy Partners L.P.

Rio Vista is a master limited partnership focused on acquiring and developing oil and gas exploration, production and transportation assets. Through its subsidiaries, Rio Vista currently owns certain leasehold interests of oil and gas producing properties and associated pipeline gathering systems in East Central Oklahoma. Rio Vista is also engaged in liquid bulk storage, transloading and transportation of chemicals and petroleum products through its assets and operations in Hopewell, Virginia. Rio Vista seeks to grow primarily through the acquisition of qualified oil and gas assets. 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 amount and timing of a distribution to unit holders. In addition, Rio Vista may not distribute sufficient cash to meet the tax obligations of unitholders associated with the ownership of common units. 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 and its registration statement on Form S-3 filed during February 2008 and in Penn Octane Corporation's most recent reports on Form 8-K, Form 10 Q and Form 10-K filed with the Securities and Exchange Commission.