Who Makes America's Dirtiest Car?

What makes one car more environmentally friendly than another? Better gas mileage, right? But that's only part of the equation. A greener auto combines fuel efficiency with lower tailpipe emissions of noxious gases like carbon monoxide, nitrous oxide, and formaldehyde.

Drawing from this logic, Forbes published its list of America's dirtiest cars and trucks. The worst? The gas-guzzling, emissions-coughing Jeep Grand Cherokee. Domestic automakers make up most of the entries on the list, with Chrysler alone responsible for five. (Tsk, Tsk.)

Forbes didn't produce a list of the cleanest cars, but hybrids boast excellent gas mileage and many have extremely low tailpipe emissions. The California Air Resources Board maintains a useful site that compares cars and trucks to others of the same year and assigns each a "global-warming score" and a "smog score," similar to how the Forbes list was drawn up.

--Année Tousseau