The real gold is in smart engine management and the use of direct injection and additives (small water or ethanol reserviors needing filled once every 5-10 tanks of gas) and/or catalyst and/or oxidizer to allow smaller engines to achieve higher compression, thus more power for less fuel. A lot of the fuel injected into the modern engine ends up unburnt and exits the exhaust as long-chain hydrocarbons. Burning more of that fuel is a win/win/win situation: Better economy/better power/lower emission of pollutants.

Beyond that, improve on management software and controlls that change the 'stroke' profile of the engine to reflect throttle demand- IE, modulate how many strokes of the piston are strokes that induce and burn gas and/or 'shut down' cylenders (such as the system chrysler has installed for some Hemi engines).

Or even better, move to turbine engine hybrids- the efficiency/weight numbers for turbines are still much better than piston engines.

Hybrids are an ok idea, but if we want to keep burning gas they have far less 'depth' as a long-term solution than just better engineering. IE- better internal combustion designs will, in the long run, have higher potential payoff than improving the hybrid idea.

Yeti