Chevrolet Volt
Chevrolet Volt

Honda Civic GX that runs on compressed natural gas topped the list of greenest vehicles of 2011, while Chevrolet Volt slipped to the last spot, according to Washington-based American Council for an Energy Efficient Economy (ACEEE).

The Chevrolet Volt “extended-range EV” sneaked through to the list as it is believed that the car's weight of nearly 3,800 pounds was a factor, though the nonprofit group did not mention the exact reason why the Volt fell short. The weight is a major factor in the rating system that indicates how much energy went into producing the vehicle.

According to ACEEE, vehicles are analyzed on the basis of a Green Score, a singular measure that incorporates unhealthy tailpipe emissions, fuel consumption, and emissions of gases that cause global warming. This year’s greenest list features 13 vehicles.

For the 8th year, the Honda Civic GX won the top honors with a Green Score of 54, followed by the all-electric Nissan Leaf and the gasoline-powered Smart Fortwo.

Hybrids Toyota Prius, Honda Civic Hybrid, and Honda Insight take the next three spots, followed closely by small internal combustion cars Ford’s new Fiesta SFE, the Chevrolet Cruze Eco, Hyundai Elantra, Mini Cooper and Toyota Yaris.

The strong showing of conventional vehicles in the top 12 is a testament to how serious manufacturers have gotten about recasting these vehicles as fuel-sippers with transmission refinements, weight savings, and sophisticated internal combustion engines, ACEEE said.

Mazda 2, which beat the Chevrolet Volt by a hair, took the 12th spot. Both vehicles have Green Scores of 48.

I find it kind of laughable, GM spokesman Rob Peterson was quoted as saying in a CNN report when told of Volt's ranking and the rational behind it. “It’s one group’s interpretation of a measurement of ‘green,’.

According to ACEEE, the Meanest list of the year is populated largely by heavy trucks and SUVs, with the Bugatti Veyron heading the list this year with a Green Score of 19. Ford Expedition (FFV) / Lincoln Navigator (FFV) occupies the last position, coming at No: 12, with a score of Green Score of 23.