Exxon Mobil Corp. , the largest U.S. oil company, said on March 26 it joined a group of auto manufacturers, energy companies and government agencies studying fuel cell vehicles in California. Exxon Mobil's decision to align itself with the California Partnership marks its latest effort to stay involved in what some call the hottest development in the energy business. The Texas-based company already has a research partnership with both General Motors Corporation and Toyota Motor Corporation studying fuel cell vehicles. Such cars, buses, and trucks would be powered by an electrochemical process creating electricity by mixing hydrogen and oxygen, cutting back on emissions. In those partnerships, Exxon Mobil is developing a gasoline processor for the fuel cells, raising the possibility that gasoline could still be used in automobiles that use fuel cells. That would keep in place the current gasoline station infrastructure -- which the industry has spent years and billions of dollars constructing -- and keep oil companies at the center of fuel marketing and profits. "Gasoline fuels for fuel cell vehicles offer the advantage of using an existing and familiar infrastructure that has been fine-tuned over 100 years," Bill Innes, president of Exxon Mobil Research and Engineering Company, said. "The fuel aspect of the fuel cell vehicle plays a crucial role for the successful deployment of this technology and its acceptance by the consumer." Exxon Mobil is hoping to bring the gasoline processor technology to the California Partnership, a group that began work in 1999 with the aim of exploring the use fuel cell cars, buses, and trucks in California. The group includes auto manufacturers such as DaimlerChrysler and Ford, energy companies such as BP Amoco, fuel cell companies such as Ballard Power Systems Inc., and government agencies ranging from the the California Air Resources Board to the U.S. Department of Energy.