According to GreenerCars.com (owned by American Council for Energy-Efficient Economy or ACEEE), the top 6 current positions for the greenest cars are held by Honda and Toyota:
1. HONDA CIVIC GX
2. HONDA INSIGHT
3. TOYOTA PRIUS
4. HONDA CIVIC HYBRID
5. TOYOTA COROLLA
6. TOYOTA ECHO
The autos include partial zero-emission vehicles (PZEV) and super-ultra-low-emission vehicles (SULEV). According to American Automobile Association's Westways magazine, the following vehicles qualify as PZEV vehicles: Ford Focus 2.3-liter, Honda Civic Hybrid, Hundai Elantra, Mazda3, Toyota Prius and Volkswagen Jetta sedan.
The cleanest of the clean cars are the electric cars and hydrogen cars as they emit zero pollutants. Next come the natural gas and hybrid vehicles, which are the next best thing to zero emissions. Ford and Chevrolet have all rolled out their own lines of trucks and SUV's that are clean burning hybrid gasoline / electric models as well.
What is clear is that with rising gas prices and vehicles that have backslid on gas mileage to the levels of the early 1980's and the general acceptance that global warming is a reality, green cars are here to stay. With any luck, we will no longer backslide as we have been doing for the past 25 years but will go forward with ever greener vehicles from here on out.