Peppier diesels, hybrids and EV's on the way!
 

Here is a good article that summarizes the current and upcoming gas saving vehicles: Will These Cars Save the Auto Industry?
Peppier diesels, hybrids, even electric motors in wheels are among new fuel-savers - Business Week

Anything diesel is a target of the US EPA. I don't see it working in long term. Plenty of currently available diesels available NOW outside the US that could be brought in immediately, but they are mandated out.