This is an excerpt from article found on the Environmental Defense Fund website.
Steps for buying a fuel-efficient car
So you're in the market for a car and want to do something about global warming. Here are the steps to take to make the greenest choice.
1. Get the right-sized car that fits your needs.
The first thing to do is identify what the primary use for your vehicle will be. If you have several children and need a car big enough to transport them to soccer practice, maybe you need a wagon or minivan. If you build houses for a living, you probably need a truck for your job. But if you own a boat, say, and take it in and out of the water just a few times a year but will use the car for everyday driving ton and from work, do you really need a truck for the other 363 days? Probably not. If you buy a smaller vehicle that fits your everyday needs, you can use the savings in gas money to rent a truck for your infrequent boat-hauling trips.
2. Find the greenest choice in your size and price range.
Once you determine the right-sized vehicle for your primary uses, use the Green Ratings to find the most environmentally-friendly models. Many models are offered with a range of trims and engines. Both fuel economy and the Green Rating depend on the particular features, so note which trims have the best ratings before you head out to your dealership. Several Web sites can help:
For one-stop shopping, use the Green Ratings on Yahoo! Autos. This unique resource, developed in partnership with Environmental Defense, provides a 1-100 rating that scores new makes and models according to their overall pollution, including global warming pollution. The Green Ratings are given along with price and other vehicle specs, making it easy to identify the greenest models that meet your other requirements.
Most car shopping sites compare models according to their fuel economy. Fuel economy is the most important criterion that determines how much heat-trapping greenhouse gas is emitted from a vehicle. Choosing a model that is just a few MPG more efficient makes a big difference in helping to fight global warming over a year of driving, and a huge difference over the many years that most cars and trucks stay on the road.
At fueleconomy.gov, find out which cars or light trucks get the best mileage and which bring up the rear, or explore your ideal mileage by class, make model or mpg rating. Fueleconomy.gov is the U.S. government's official guide for information on gas mileage, and it also offers information on fuel-saving driving and maintenance practices.
Environmental ratings for some recent model years can be found on Greenercars.com, a by the independent research group American Council for an Energy-Efficient Economy (ACEEE). It's Green Scores are similar to the Yahoo! Green Ratings, though scaled differently, Greenercars.com gives highlights of the "greenest" and "meanest" recent models free, and a subscription gives access to even more information.
3. Consider whether you need options that add cost and detract from fuel economy.
Four-wheel drive increases fuel consumption, so if you don't need or use it, don't buy it.
Avoid add-ons like luggage racks that add weight and/or drag, or get removable ones so you can use them only when needed.
A souped-up engine guzzles gas and adds to global warming. All engines in today's market provide plenty of power for safe and responsible driving. Not playing along with the "horsepower war" will decrease pollution and save money on car payments and at the pump.