Why American Automakers Aren't Producing More 'Clean Diesel' Cars

German automakers like Volkswagen, BMW and Mercedes, and Japanese automaker Mazda said this week at the North American International Auto Show that they are planning to offer more vehicles that run on "clean" diesel.

U.S. automakers, though, say they won't offer diesel engines in anything but heavy-duty work trucks because they don't see consumer demand, nor, they say, can they price their vehicles high enough to pay for diesel systems.