Quote:
Originally Posted by tballx
Fair enough. I was paraphrasing too literally. Double it to 30% if you like. I think the study at least pretty clearly shows that continuing to operate a vehicle of lesser efficiency just because it will run will not minimize your carbon impact and that moving from a car that gets 20mpg to a car that gets 35mpg is desirable if you have the means to do so.
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First, 20->35mpg is an improvement of 75%, not 30%. Even then, going from 20mpg to 35mpg wouldn't reach a break even until the new car had been driven for 64,000 miles.
However, the energy and material requirements from the PDF are a projected estimate of a car built in 2020. So all of these calculations are at best rough estimates.
I think the take away is that even with a substantial improvement in fuel economy (and 20 to 35mpg is substantial) a vehicle needs to be used for a substantial amount of time for it to offset its creation costs.