General Motors Corp., having won the first round of its fight to stave off significantly tougher federal fuel-economy standards, is quietly planning a push to weaken the nation's clean-air rules to allow wider use of diesel engines as fuel-saving alternatives to thirsty gasoline light-truck engines, according to a story by Jeffrey Ball in the Wall Street Journal. The world's biggest automaker is taking its pro-diesel campaign public with a report scheduled to be issued Aug. 6 by the Diesel Technology Forum, a trade group based in Herndon, Va. GM is the only automaker in the group, which includes manufacturers of diesel engines and diesel-system components, as well as Exxon Mobil Corp., the Irving, Texas, oil company. The report points out that although diesels accounted for less than one percent of new car and light-truck sales in the U.S. for 2000, they are surging in popularity in Western Europe, where they constituted about one-third of new sales. Diesels can get at least 30 percent better fuel economy than comparably sized gasoline engines -- an important advantage in Europe, where gasoline prices are high. Tax policies in some European countries encourage diesel use, but so do European clean-air standards, which are more lenient than a new round of U.S. rules toward the pollutants associated with diesel motors. These new clean-air rules in the U.S., the report claims, "constitute a significant challenge for the future of diesel vehicles in America." GM officials say they hope to persuade government officials to take a hard look at those regulations, set to take effect starting in 2004.