mmmm... most of the ones I wanted to say have already been covered:
- transmission gear ratios
- aerodynamic front molding/design
- underbelly smoothing
- on-board FE feedback system
I think some car makers are doing these, but not for every car. I believe it was Mercedes who modded their C-class down to a 0.25 Cd:
http://ecomodder.com/forum/showthrea...oday-4736.html