Hey all. I need to buy a new car, and am primarily interested in buying something that has as minimal an impact as possible on the environment over the lifespan of the car (car manufacturing, fuel production impact, lifetime driving, disposal).

So, my question is: Which one is cleaner? Biodiesel (e.g. a Jetta TDI), or a hybrid such as a Prius or a Civic? I'll be driving in pretty typical city conditions.