Re: Energy in = energy out
You've a very long wait indeed for that. The most efficient engines mankind has devised are approaching 50% efficient. You're not likely to find one that good in a car any time soon, they weight a couple of hundred tonnes and power megaships. Wikipedia says 25-30% for petrol and I guess a bit better for diesel at the car scale so most of our money is still wasted as heat.
Correction after fact check; couple of thousand tonnes. Look up Wartsila-Sulzer RTA96-C.