Jim @ 23:

with my manager hat on: any difference is way, way too small to be detectable; this is not a decision factor

with my engineer hat on: almost certainly better to keep driving what you have, because the carbon footprint from manufacturing the new vehicle will outweigh any savings from improved mileage, but – you didn’t mention the Suburban MPG (12-15?), or how many miles you expect to drive over the next ten years, or the MPG you anticipate from the replacement vehicle, so one can’t really run the numbers.

One might also consider a third option – wait a couple of years and buy the likely even better vehicle available then, after getting full use out of your current Suburban. I suspect that is the optimum solution from a footprint perspective, and – amazingly – the solution that one would be pointed toward purely on the basis of personal economics.

There have also, I believe, been some studies that show that the total impact from electric vehicles (manufacturing, battery replacement, power generation) is pretty similar to modern internal combustion vehicles.