Diesels are back! During the past six years, more than 2.5 million new diesel-powered cars and light trucks have been sold in the United States. Though the numbers are not huge, they are growing. Diesel usage in U.S light vehicles has almost doubled over the last five years (from 2.2% in 1999 to 3.9% in 2004), and experts predict that diesel usage will probably double again and grow to as much as 8-15% of the passenger car/light truck market over the next decade.

Diesels have long been a popular option in pickup trucks for their stump-pulling power and good fuel economy. Current trucks with diesel options include Chevy Silverado, GMC Sierra, Dodge Ram, Ford E-Series, F-Series and Excursion. A diesel-powered Jeep Liberty is also available this year, but it will be a limited production offering (only about 5,000).

As for passenger cars, currently there are no diesel-powered domestic models. Volkswagen and Mercedes-Benz are currently the only manufacturers who are offering diesel options. VW offers diesels in its Passat, Golf, Jetta and Beetle cars, and the Touraeg sport utility vehicle. Mercedes recently added a diesel option for its E 320 Class luxury sedans, with more models to come later this year.

Diesels Are Different
Compared to gasoline engines, diesels have a number of important advantages. One is fuel economy. Diesel engines are unthrottled so pumping losses are reduced. This improves breathing eff...