The Cleanest Cars on Earth: Honda Civic GX and Other Natural Gas Vehicles (NGVs) : Gas 2.0

Clean Burning Natural Gas Vehicles (NGVs) are hot commodities in some parts of the country, where fuel can sell for as low as $0.63 per gallon. This Civic NGV is powered by the simplest and cleanest-burning hydrocarbon available, and though it looks like a standard passenger vehicle, its tailpipe emissions that are often cleaner than ambient air.