Find Green Cars

Efficient Cars:
Annual Fuel Cost Calculator
Enter the make, year and model to find your average annual fuel cost. This site is run by the U.S. Department of Energy in conjunction with the U.S. Environmental Protection Agency.
-- From FuelEconomy.gov 

Efficient Cars:
Hybrid Vehicles Gas Saving Calculator
Use the calculator to view your fuel savings and impact on the environment.
-- From MixedPower.com 

Efficient Cars:
Vehicle Life-Cycle Cost Comparison
Enter your car's model and get a graph comparing its life-cycle cost and greenhouse gas emissions against similar vehicles.
-- From Canada Office of Energy Efficiency 

Clean Cars:
EPA Green Car Guide
Use this guide to choose the cleanest cars. Low-emissions cars usually have the best fuel economy, too. Save the environment and save on gas!
-- From Environmental Protection Agency 

Clean Cars:
Vehicle Emission Control Information
Do you know where to find it on your car? Is it on the window sticker? Or under the hood? Or in front on the radiator shroud?
-- From FuelEconomy.gov