Rio Vista Energy Partners L.P. Announces Signing of Amended and Restated Agreement to Sell Certain LPG-Related Assets.

HOUSTON -- Rio Vista Energy Partners L.P. (NASDAQ:RVEP), a supplier of LPG for distribution to northeast Mexico, announced today that it had entered into an amended and restated purchase and sale agreement (Rio Vista Restated PSA) with TransMontaigne Product Services Inc. (TransMontaigne), a wholly owned subsidiary of TransMontaigne Inc. (NYSE:TMG). In connection with the Rio Vista Restated PSA, Penn Octane Corp. also entered into an amended and restated purchase and sale agreement (Penn Octane Restated PSA) with TransMontaigne. The restated PSAs replace the previously executed purchase and sale agreements between Rio Vista, Penn Octane and TransMontaigne dated Aug. 15, 2005.

The Rio Vista Restated PSA is effective Aug. 15, 2006, and provides for the sale and assignment of Rio Vista's LPG assets located at the Brownsville Terminal Facility, the refined products tank farm and LPG inventory wherever located and assignment of the P.M.I. Trading Limited sales agreement dated April 28, 2006. Rio Vista will retain its owned pipelines located in the United States, including land, leases, and rights of way, and 100 percent of the outstanding stock of its Mexican subsidiaries. Rio Vista's Mexican subsidiaries and consolidated affiliate in turn own pipelines in Mexico and the Matamoros Terminal Facility, including land and rights of way. The purchase price for the acquired assets under the Rio Vista Restated PSA is $8,300,000, subject to certain adjustments. In addition, under the Rio Vista Restated PSA, TransMontaigne has agreed to exclusively use the services and retained assets of Rio Vista on a fee basis for purposes of transportation of LPG to be delivered into northeastern Mexico and/or LPG sold pursuant to the PMI sales agreement. In addition, under the Rio Vista Restated PSA, TransMontaigne agreed to provide operation and maintenance services for the U.S. portion only of Rio Vista's pipelines between Brownsville, Texas, and Matamoros, Mexico. The Rio Vista Restated PSA provides for a closing no sooner than Aug. 22, 2006, and is subject to several conditions, including concurrent closing of the Penn Octane Restated PSA, assignment of LPG-related contracts, the consent of RZB Finance LLC and the modification satisfactory to TransMontaigne of a temporary injunction issued on June 13, 2006, against one of Rio Vista's subsidiaries. The Rio Vista Restated PSA also provides that either party may terminate the agreement if closing does not occur on or before Oct. 1, 2006.

The Penn Octane Restated PSA is effective Aug. 15, 2006, and provides for the sale and assignment of all of Penn Octane's LPG assets, including assignment of the Seadrift Pipeline Lease and the Exxon Supply Contract. Penn Octane will retain assets related to its Fuel Sales Business and its general partner interest in Rio Vista. The purchase price for assets to be sold under the Penn Octane Restated PSA is $10,100,000, subject to certain adjustments. The Penn Octane Restated PSA provides for a closing date no sooner than Aug. 22, 2006, and is subject to several conditions, including concurrent closing of the Rio Vista Restated PSA, the assignment of LPG-related contracts, the consent of RZB Finance LLC and the modification satisfactory to TransMontaigne of a temporary injunction issued on June 13, 2006, against one of Rio Vista's subsidiaries. The Penn Octane Restated PSA provides that either party can terminate the agreement if closing does not occur on or before Oct. 1, 2006.

About Rio Vista Energy Partners L.P.

Rio Vista Energy Partners L.P. ("Rio Vista") is an energy services master limited partnership that owns or operates Liquefied Petroleum Gas (LPG) assets in southeastern Texas and northeastern Mexico. The partnership seeks to grow through the acquisition of qualified oil and gas assets. All of Rio Vista's common units were distributed to the stockholders of Penn Octane Corp. ("Penn Octane") on Sept. 30, 2004.

Forward-Looking Statements

Certain of the statements in this news release are forward-looking statements, including statements regarding the completion of the proposed LPG asset sale and the possible future acquisition 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. The proposed LPG asset sale may not be completed if any of the conditions to closing, including the modification of a temporary injunction issued against one of Rio Vista's subsidiaries, are not satisfied or if various governmental and third-party approvals are not obtained. If Rio Vista does not have sufficient capital resources for acquisitions or opportunities for expansion, Rio Vista's growth and its ability to pay quarterly distributions will be limited. Rio Vista does not have sufficient available cash to pay minimum quarterly distributions to common unitholders. Rio Vista may be unable to complete future acquisitions of qualified oil and gas assets and, even if completed, such acquisitions may not prove successful. 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.