BMW just
anounced that they've developed a hybrid "Turbosteamer" engine that operates off of the heat given off from a gasoline burning engine. This development adds 15% efficiency, and reduces emissions by 80%. The best part? They've designed it modularly so that it can be added to any existing BMW. (Sadly, they're not ready to sell it yet.)
Since the technology could feasibly work in conjunction with a gas-electric hybrid, the geek in me really wants to see what kind of mileage I'd get if I could add one to my Prius.