You'll be a long time making up the energy emissions of building and buying a new efficient (or electric) vehicle over using a relatively low-emissions vehicle like a Civic. Granted, that Civic would probably be used by someone else that isn't going to then buy a new car, but keeping existing vehicles running is more efficient than making new ones constantly.

Again, looking at systems from top to bottom and not focusing on individual elements makes more sense, though it's not easy. This is why hydrogen powered vehicles make no sense if you need to use fossil-fuel energy to make hydrogen, or take away clean energy from other users to do the same.

By far, the best option is to use solar energy already falling on the earth to generate electricity, but then storage and the high environmental costs of mining rare-earth elements used in solar cells becomes a factor, as well as building distribution networks to get it from where it's made to where it's used.