With a green score of 54, the Civic GX earned the number one ranking on ACEEE's "Greenest Vehicles of 2011." Yes, the battery-powered Nissan Leaf did score 54, same as the Civic GX, but ACEEE's ranking system places more emphasis on pollution than fuel economy and that's why the CNG-fed Civic retained the top spot.
The plug-in hybrid Chevrolet Volt, a no show in the top ten, ranked twelfth overall. The Volt's poor showing was due, at least in part, to its hefty curb weight and comparatively poor fuel economy when operating in range-extended mode.
The pint-sized Smart Fortwo, with its 1.0-liter gas engine, placed third overall, trailing the Leaf and the Civic GX by one point. The world's best-selling hybrid, the Toyota Prius, captured fourth and two more Hondas, the Civic Hybrid and the Insight, ranked fifth and sixth, respectively.
ACEEE's ratings are based on a weighted score that's derived from fuel efficiency ratings, weight, emissions and complex formulas used to calculate a vehicle's overall environmental impact.
[Source: Greener Cars]