DETROIT -- The company most responsible for putting the sport in sport sedan is on the diesel bandwagon. BMW this week unveiled a pair of low-emissions diesel engine vehicles based on the 3 Series compact sport sedan and the X5 sport utility vehicle. The 335d sedan and X5 xDrive35d (photo) SUV (BMW calls it SAV, or sports activity vehicle) will be available this fall with performance on par with gasoline-engine BMWs and fuel economy about 20% higher. Both use a six-cylinder engine with two turbochargers producing 265 hp. "It is the cleanest diesel engine with the sportiest and best performance - in the world," said Dr. Norbert Reithofer, BMWs chairman, at the North American International Auto Show. Mercedes-Benz beat BMW to market by a year with the Bluetec diesel engine on vehicles such as the GL320 SUV. . While Bluetec was a low-emissions engine, it wasn't low enough to meet emissions standards in all 50 states (California and several northeastern states have stricter limits). BMW opted to wait a year until technology came available that made diesels 50-state legal on emissions.

While hybrids get a lot of publicity for their efficiency, diesels are the most efficient powerplants - better than gasoline, better than hybrids - for highway cruising. Plus, there's nothing to stop an automaker from creating a hybrid with a diesel not gasoline engine. BMW says diesels account for 40% of its sales worldwide and about 60% in Europe.