In 1976 it was the Dodge Aspen.

FORBES: Chevrolet: Where Federal Subsidies Run Deep

Of American automakers, though, Chrysler is the worst offender, with six vehicles on last year's "dirtiest" list (the Jeep Commander, Jeep Grand Cherokee, Dodge Durango, Chrysler Aspen, Dodge Ram 1500 and Dodge Dakota), and five this year.

FORBES: Vehicles

Some examples: the Jeep Patriot and Jeep Compass compact SUVs, or the Dodge Durango and Chrysler Aspen SUVs.

FORBES: Companies, People, Ideas