Compared to gasoline, compressed natural gas (CNG) is cleaner, less expensive, and generally comes from domestic reserves. However, CNG vehicles also require some compromises, including the use of a special refueling infrastructure that is not widely developed in the United States.

CNG vehicles store natural gas in pressurized tanks and burn the gas in slightly modified internal combustion engines. Natural gas, which is 90 percent methane, has a much higher octane rating than gasoline, allowing for higher compression ratios and therefore greater efficiency in the engines that use it. Natural gas burns so cleanly that CNG vehicles rival hybrids in producing extremely low levels of smog-forming pollutants. However, CNG vehicles tend to have higher greenhouse gas emissions than hybrids.

The 2009 Eclipse Spyder is a 2-door, 4-passenger convertible, or convertible sports car, available in two trims, the GS and the GT.

Upon introduction, the GS is equipped with a standard 2.4-liter, I4, 162-horsepower engine that achieves 19-mpg in the city and 26-mpg on the highway. A 5-speed manual transmission with overdrive is standard, and a 4-speed automatic transmission with overdrive is optional. The GT is equipped with a standard 3.8-liter, V6, 265-horsepower engine that achieves 16-mpg in the city and 25-mpg on the highway. A 6-speed manual transmission with overdrive is standard, and a 5-speed automatic transmission with overdrive is optional.

The 2009 Eclipse Spyder is a 2-door, 4-passenger convertible, or convertible sports car, available in two trims, the GS and the GT.

The 2009 TT is a 2-door, up to 4-passenger luxury sports coupe, or luxury convertible, available in 8 trims,ranging from the 2.0T With S tronic to the 3.2 Roadster quattro with S tronic.

Upon introduction, the 2.0T With S tronic is equipped with a standard 2.0-liter, I4, 200-horsepower, turbo engine that achieves 23-mpg in the city and 31-mpg on the highway. The 3.2 Roadster quattro with S tronic is equipped with a standard 3.2-liter, V6, 250-horsepower engine that achieves 18-mpg in the city and 24-mpg on the highway. A 6-speed automatic transmission with overdrive is standard on both trims.