Rio Vista Energy Partners Enters into Letter of Intent to Sell Remaining LPG Assets.

BROWNSVILLE, Texas -- Rio Vista Energy Partners L.P. (NASDAQ: RVEP), an energy services master limited partnership ("Rio Vista"), announced today that it has signed a binding letter of intent with TransMontaigne Partners L.P. ("TLP") to sell to TLP Rio Vista's terminal

facility in Matamoros, Mexico, two pipelines, with associated rights of way and easements, from the Brownsville, Texas terminal owned by TLP to the Matamoros terminal facility and related permits (collectively, "LPG Assets"). The total purchase price for the LPG Assets is $10.5 million, subject to adjustments at closing, and is contingent on execution of a definitive purchase and sale agreement and completion of due diligence satisfactory to TLP. The transaction is expected to close during the fourth quarter of 2007. In connection with execution of the letter of intent, Rio Vista received a refundable deposit of $6.5 million from TLP.

Rio Vista intends to use the deposit as well as proceeds to be received upon the closing of the sale of the LPG Assets to make additional acquisitions of qualified oil and gas assets. As previously announced, Rio Vista has entered into letters of intent to acquire interests in certain oil and gas producing properties and associated pipeline gathering systems from four privately held companies based in East Central Oklahoma.

"The proposed sale of the LPG Assets represents a shift of Rio Vista's operations to US-based energy related projects, including oil and gas producing properties," said Ian Bothwell, Acting Chief Executive Officer of Rio Vista's general partner. "We expect the deposit received in connection with the proposed sale of the LPG Assets to provide additional capital required by Rio Vista in connection with several acquisition opportunities. In addition, upon the sale of our Mexican related operations, management will be able to shift their efforts towards the development and operation of domestic oil and gas producing properties and related projects".

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. It currently owns certain liquefied petroleum gas assets, including pipelines running from Brownsville, Texas to a terminal facility in Matamoros, Mexico owned by Rio Vista. 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.

Forward-Looking Statements

Certain of the statements in this news release are forward-looking statements, including statements regarding the closing of the sale of LPG Assets to TransMontaigne Partners L.P., the closing of the purchase of oil and gas interests in East Central Oklahoma and other possible acquisitions of qualified oil and gas 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. These risks include the fact that the closing of these transactions may take longer than anticipated or may not occur if conditions to closing are not satisfied, Rio Vista may be unable to complete other acquisitions of qualified oil or gas assets, and Rio Vista may be unable to pay future distributions. Even if completed, future acquisitions and expansions may not be successful, may dilute the interests of unitholders, may substantially increase Rio Vista's indebtedness and contingent liabilities, and may present integration difficulties. If Rio Vista does not have sufficient capital resources for acquisitions or opportunities for expansion, its growth and ability to pay quarterly distributions will be limited. 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 10 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.