Rio Vista Energy Partners L.P. Receives Nasdaq Notification.

HOUSTON -- Rio Vista Energy Partners L.P. ("Rio Vista") (NASDAQ: RVEP), an energy services master limited partnership, announced today that the Company received, on July 2, 2007, an acknowledgment (the "Acknowledgment") from the Nasdaq Stock Market ("Nasdaq") regarding Rio Vista's notification to Nasdaq dated June 18, 2007 of a vacancy on the audit committee of the board of managers of Rio Vista GP LLC (the "General Partner"), the general partner of Rio Vista. This vacancy arose on June 15, 2007. Nasdaq Rules 4360(d) and 4350(d)(2)(A) require the General Partner to have an audit committee of at least three members. The General Partner currently has two members of its audit committee. As set forth in the Acknowledgment, pursuant to Nasdaq Rule 4350(d)(4)(B), Rio Vista has until June 15, 2008 to regain compliance with Nasdaq's audit committee requirements. The General Partner intends to fill the vacancy on the audit committee on the earliest practicable date.

About Rio Vista Energy Partners L.P.

Rio Vista is an energy services master limited partnership that owns certain liquefied petroleum gas assets, including pipelines running from a terminal facility in Brownsville, Texas owned by TransMontaigne Product Services, Inc. ("TransMontaigne") to a terminal facility in Matamoros, Mexico owned by Rio Vista. Pursuant to an LPG Transportation Agreement with TransMontaigne, Rio Vista uses its assets to transport LPG exclusively for TransMontaigne on a fee-for-services basis. Rio Vista seeks to grow through the acquisition of qualified oil and gas assets and other assets. All of Rio Vista's common units were distributed to the stockholders of Penn Octane Corporation ("Penn Octane") on September 30, 2004.

Forward-Looking Statements

Certain of the statements in this news release are forward-looking statements, including statements regarding the intention of the General Partner of Rio Vista to fill a vacancy on the audit committee of the General Partner, the prospects for the LPG transportation business and the possible acquisition of qualified oil and gas assets and other assets. Although these statements reflect Rio Vista's beliefs, they are subject to uncertainties and risks that could cause actual results to differ materially from expectations. Rio Vista may experience unanticipated difficulty in attracting qualified candidates to serve on the board of managers and audit committee of its General Partner. If Rio Vista is not able to obtain adequate financing and does not receive sufficient revenues from the use of its retained LPG assets, Rio Vista would suffer material adverse consequences to its business and will not have sufficient available cash to pay minimum quarterly distributions. If Rio Vista does not have sufficient capital resources for acquisitions or opportunities for expansion, Rio Vista's growth will be limited. Rio Vista may be unable to complete future acquisitions of qualified oil and gas assets or other transactions and, even if completed, acquisitions may not prove successful. The tax consequences of ownership of common units are dependent on the specific tax circumstances of each unitholder, and Rio Vista may not distribute sufficient cash to meet the tax obligations of unitholders. Additional information regarding risks affecting Rio Vista's business may be found in Rio Vista's registration statement on Form 10 and its reports on Form 8-K, Form 10-Q and Form 10-K and Penn Octane's reports on Form 8-K, Form 10-Q and Form 10-K filed with the Securities and Exchange Commission.