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Are "clean diesels" ready to join good hybrids as a clean vehicle option?
10/04/06

Patricia Monahan, Senior Vehicles Analyst for UCS here.  I work primarily on diesel issues, and car manufacturers are racing to produce diesel cars that can meet new tailpipe standards coming into full effect in 2009. Honda, Mercedes-Benz, DaimlerChrysler and VW are all planning on selling diesel cars, touting their 20 to 30 percent superior fuel economy over comparable gasoline models. That could be good for consumers who want vehicles that travel further on a gallon of fuel and have lower greenhouse gas emissions.

But it's important to do the right math when it comes to diesel fuel. A gallon of diesel fuel takes more oil to produce and it produces more greenhouse gases than a gallon of reformulated gasoline (with ethanol). This means you should cut the diesel fuel economy by as much as 15% when comparing it to a gasoline model.

We're also not sure how the first generation of so-called "clean diesels" are going to perform on the road. Diesel cars don't have sophisticated pollution monitors—like gasoline vehicles do—to catch systems when they fail.  So long-term use and emissions impact is still very much up in the air. In all, there are reasons to be both excited, and wary, about the new diesel cars we'll soon be seeing on the market.

Posted by: Patricia 10/04/06

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