Honda Civic GX

The Civic GX, which runs on compressed natural gas, gets the ACEEE's accolade of greenest of the green. Mileage figures of 30mpg (city) and 34mpg (highway) are propped up by the car's EPA emissions rating, which is the lowest of all vehicles on the road. As well as being certified as an advanced technology partial zero emissions vehicle (AT-PZEV), the GX also is rated by the EPA as an inherently low emissions vehicle (ILEV), meaning it conforms to standards for zero evaporative emissions.