The Department of Energy's vehicle cost calculator is an excellent to way to check the environmental impact of a used car you want to buy. It's also going to help you easily compare used cars to see which is the most environmental and/or economical and have the best environmental footprint.
The vehicle cost calculator was developed by the Department of Energy's Alternative Fuels and Advanced Vehicles Data Center.
Commonly known as the AFDC, it is a comprehensive clearinghouse of information related to advanced transportation technologies. The AFDC was originally developed in 1991 in response to the Alternative Motor Fuels Act of 1988. Since then, the AFDC has expanded its focus from alternative fuels to include an array advanced transportation fuels, vehicles, and other emerging technologies.
How it works is you go to the AFDC website for its vehicle cost calculator. You can plug in information on up to eight cars going back to 1997. You can't quite plug in all makes and models but you can plug a lot. (See below to see what two prominent brands didn't make the cut.)
For comparative reasons, I looked at four fairly common crossover utility vehicles from 2005: the Ford Escape AWD, the Chevrolet Equinox AWD, the Dodge Durango AWD, and the Toyota Highland AWD. They're fairly similar used SUVs that I would cross shop if I was in the market.
The graph that results from comparing vehicles is handy and easy to read.
According to the website, it shows the cumulative cost of ownership by year for each vehicle, including fuel, tires, maintenance, registration, license, insurance, and loan payment. The tool assumes a five-year loan with a 10% down payment. Year one on the graph represents the 10% down payment plus the first year's total operating costs.
A plus for the site is it allows you to post your specific driving habits. My 2008 Mazda5, for example, doesn't travel a lot because I also review new cars. So, I could put in its approximately 5000 annual miles and see what it costs me annual to run it.
One caveat when it comes to the costs is they are based on the assumption that fuel costs remain static. Don't use the final figure to determine what your final costs are going to be. This chart is best used for first-year comparisons on costs and environmental impact.
How It Works
Advanced mathematics has never interested me (and that explains why I became a writer and not an actuary). However, if it's your cup of tea, you should check out the vehicle cost calculator assumptions and methodology page. It shows how all of the data is computed, especially with hybrids, plug-in hybrids, and flex fuel vehicles.
One of the problems with the site (and it's really a minor nitpick) is it doesn't have pricing data for used cars more than two years old. Seems as if the U.S. government would have the resources behind it to obtain the pricing data. It already has a partnership with Edmunds.com, via FuelEconomy.gov, on city and highway fuel economy numbers. (By the way, who knew that the federal Environmental Protection Agency sourced information from Edmunds?)
Also, you're out of luck if you want to check on a used Hummer or Oldsmobile for comparison. They may no longer be in business, but neither are Pontiac or Saturn and they both made the cut. The used car comparisons do go back to 1996 when both companies were still in business. However, in all honesty, if you're searching for a used Hummer, you're probably not that concerned about fuel economy and environmental effects.
Don't Stop Here
Of course, this is only one tool to use when used car shopping. You're still going to want to check out Consumer Reports reliability rankings. (They're not perfect but they are a good indication of potential problems.)
Also, before signing on the dotted line, make sure you get a used car inspection. Tools like this calculator are only one part of the overall used car shopping equation.