We all want to be a little greener. And it seems like the best way to be green when it comes to cars is to to buy a new state of the art hybrid with excellent gas mileage, right? I mean, obviously a Prius is better than say a 1998 Honda Civic. Well, maybe not. According to this article in Wired, the Prius comes to you in carbon debt because of the energy used to make it. Just to work off this debt it will take about 46,000 miles of driving. Also take into account the fact that a used car has already worked off its carbon debt. So now depending on gas mileage of the used car you are considering, that Prius will have to go another 100,000 miles before it catches up! Phew that is a lot of driving. The articles points to a few cars as having very good gas mileage but also links to this handy site to compare models. New is shinier, but not always better.
iamlizbeth.com 
Hey thanks for this post eliz. Alan and I have been debating this as we search for a newer car and the article will lend some insight into the situation.
I appreciate your effort to keep true to your tastes while being earth-conscience!