The American Council for Energy Efficient Economy (ACEEE) has been publishing its Green Book ratings for year, so I looked forward to reading their rankings of green cars. The organization uses SAE standards and takes a wide range of pointers into consideration beyond mileage ratings. Surprisingly, the natural gas-powered Honda Civic GX narrowly beat out the Nissan Leaf for No. 1. Even more surprising , the Chevy Volt hit No. 12 on the list, after sweeping a few awards recently like Green Car of the Year from Green Car Journal. A large factor in the rating is the car's weight, and the Volt is a heavy car, sort of a muscle car PEV. They also factored in a ratio of the car typically running 64% of time on electricity and 36% on gasoline, and the gas part of the trip doesn't get great fuel economy.