The Honda Civic GX natural gas car has been recognised as the most environmentally-friendly car on sale in America by the American Council for an Energy-Efficient Economy (ACEEE).

This the fifth consecutive year that the car has ranked top of the annually-produced listing marketed as Green Book Online (

Honda said it was the eighth year in a row it had topped the ranking and that is also held three of the other top 12 positions.

The ACEEE analysis is based on automakers' test results for fuel economy and emissions as reported to the US Environmental Protection Agency and the California Air Resources Board, along with other specifications reported by automakers.

It then estimates pollution from vehicle manufacturing, from the production and distribution of fuel and from vehicle tailpipes. The scoring is based on air pollution, such as fine particles, nitrogen oxides, hydrocarbons plus greenhouse gas emissions.