• Honda's Civic GX should be hitting showrooms by the fall of 2011.
• It runs on compressed natural gas with a range of 250 miles on a single tank of fuel.
• It's described as the cleanest car in the United States in terms of total environmental impact.

The greenest car you've likely never heard of will soon be hitting Honda showrooms across the United States as the Japanese automaker expands sales of its compressed natural gas-powered Civic.

Honda has been quietly winning green car awards for more than a decade as it cautiously introduced the Civic GX first to government and business fleet owners and then retail customers in a handful of test markets.