Aramco Services Company

Malaysian Refining Co.

Ashland Petroleum Company

Mitchell Energy Corporation

ARCO Products Company

Mobil Oil Canada

BHP Hawaii, Inc.

Mobil Oil Exploration & Production Southeast, Inc.

BP Amoco

Navajo Refining Company

Burlington Industries

New Grade Energy

CEPSA

Pacific Offshore Pipeline Company

Champlin Petroleum Company

Pemex Gas & Petroquimica Basica

Chevron Canada Limited

Petro-Canada

ChevronTexaco Products Company

Phillips 66 Natural Gas Company

Chevron U.S.A. Inc.

Placer CEGO Petroleum

CITGO Petroleum

Premcor Refining Group

Clark Refining & Marketing, Inc.

Qatar Gas

Conoco, Inc.

SARAS S.p.A.

Conoco Limited (U.K.)

Saudi Arabian Oil Company (Aramco)

Crescendo Energy (Maxus)

Sid Richardson Carbon & Gasoline Company

Delhi Gas Pipeline Corporation

Shell Canada, Ltd.

Destec Energy, Inc.

Shell Oil Company

Dow Chemical Company (U.S.A.)

Star Enterprise

Dubai Natural Gas Company

Suncor Energy Inc.

Duke Energy Field Services

Syncrude Canada, Ltd.

Empresa Nacional del Petroleo, S.A. (Spain)

Sulconam, Inc.

ERT Petroleo

Tenneco Oil Company

Excel Paralubes, Inc.

Tessenderlo Kerley, Inc.

Exxon Company, USA

Tesoro Alaska Petroleum

ExxonMobil

Texaco

Fina Oil & Chemical Company

TengizChevroil LLP

Husky Oil Company

TOSCO Corporation

Imperial Oil, Ltd.

Total Petroleum, Inc.

INDEVEN, S.A.

Ultramar Inc.

Jupiter Sulphur

Ultramar Canada, Inc.

Kerr-McGee Corporation

United Refining

Koch Midstream Services

Union Oil Company of California (Unocal)

Kuwait National Petroleum Company (K.S.C.)

Valero Refining Company

La Gloria Oil and Gas Company

VECO

Louisiana Land & Exploration Company

Williams Energy Services

Lyondell Citgo Refinery Co.