Modern cars are inefficient. Even hybrid cars are inefficient. All internal combustion engines are inefficient.
Internal combustion engines work on the explosive force from burning the fuel. External combustion engines work purely on the heat created by burning the fuel. Huge amounts of heat are wasted in internal combustion engines, since all they do is pump the heat into a radiator to dissipate. And no energy at all is taken from the expanding force of burning fuel in an external combustion engine.
It's ridiculous - why has no one thought to combine the two?
The closest thing I've seen to it is the so-called "six stroke cycle". Here, instead of a cooling system, cold water is pumped into the pistons each stroke, and the heat causes it to evaporate, driving the piston down for another stroke. This is apparently as much as 40% more efficient than a standard 4 stroke. However, obviously, it needs a cool supply of water to function, so it's only suited for things like power stations and so on.
My proposal doesn't mean a complete redesign of the car engine. All I'm saying is, use the mechanism from a Stirling engine (an external combustion engine) to cool the body of your standard internal combustion engine. There'd be no need to make complicated gear boxes to take two sources of power, it could be just as simple as the main engine driving the wheels, the Stirling engine charging the battery and electrics.
This would be even easier to implement into a hybrid car.
If you can't see the benefit of doing this, well, there's not much I can say to persuade you. I guess I'll just have to build a working prototype, which won't be for a while.