Just because a car has low fuel efficiency doesn't mean it's the worst polluter on the road. The Chevrolet Suburban and Dodge Challenger are some of the biggest gas-gulpers available, but they don't cause quite the environmental harm other cars do.
That title is reserved for vehicles that combine their poor gas mileage with high tailpipe and greenhouse gas emissions. Think along the lines of some of the bulkiest cars on the road, like the Jeep Grand Cherokee, Chevrolet Trailblazer and Dodge Dakota.
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To determine the dirtiest cars on America's roads, we used air pollution and greenhouse gas emissions data from the U.S. Environmental Protection Agency.
1. Jeep Grand Cherokee
2. BMW M5
3. BMW M6 Sedan/Convertible
4. Chevrolet Trailblazer
5. Mercedes-Benz CL600
6. Mercedes-Benz S600
7. Chrysler Aspen
8. Dodge Dakota
9. Dodge Ram 1500
10. Dodge Durango
http://autos.yahoo.com/articles/autos_content_landing_pages/1159/americas-dirtiest-vehicles/