Previously we listed the 10 most environmentally-friendly vehicles as determined by Forbes magazine. Now we go to the smoggy side to find the 12 worst polluters. Our source, this time, is the Green Book issued by the American Council for an Energy-Efficient Economy (ACEEE).

Each year, the ACEEE reviews vehicles and gives it a Green Score: the vehicle's overall environmental impact. The Green Score is based on fuel efficiency, tailpipe emissions, and vehicle gases contributing to global warming. Those with the worse scores are considered "mean" machines.

The worst top 12 Mean Machines from "least" worse to "most" worse are:
  1. Dodge Ram SRT-10
  2. Lamborghini Murcielago
  3. Bentley Arnage
  4. Dodge Durango 4.7 V8 4WD
  5. Dodge Ram 1500 4.7 V8 4WD
  6. Maybach 57S
  7. Hummer H2
  8. Ferrari 599 GTB Fiorano
  9. Ford F-250 Super Duty 5.4 V8 4WD
  10. GMC Yukon XL 2500 4WD
  11. Volkswagen Touareg V8 (pictured)
  12. Chevrolet Suburban 2500 4WD
[Source: ACEEE's Green Book Online via MSN Autos]