On the subject of fuel economy, how about a full-sized truck that gets 60 mpg like a Prius? Plus, there are no batteries or electric motors.
Hydraulic hybrids make perfect sense to me, even if just to fill the gap between now and when we can do away with gas engines altogether.
Check it out:
http://www.planetblueoval.com/ford/f...t_1_000599.asp