I've long thought that a good diesel electric drive would be great to use in automobiles. A good diesel will last pretty much forever. If the thing is running at optimal output all the time that it is on, it seems like it would be a real win. The big problem is conversion losses. Every time you convert energy from one form to another, you lose some. Thermodynamics simply won't allow anything else.
My dad owns a diesel VW that gets crazy mileage...but with the emissions ‘scandal’, I believe diesels (in the US) will suffer a setback, and newer models will probably get poorer mileage in order to reduce emissions.
If I were much, much smarter, I would find a way to scavenge all the heat lost in an engine.