Internal combustion has never been efficient. In fact, during the Victorian era, it was rejected in favor of steam power because of the rarity of petroleum. It's only these days, thanks to the abundance of oil from places like the Middle East that we can efficiently run on gasoline.
Even with readily available sources for the combustible fuel, the act of using it to power our cars produces a lot of excess heat that doesn't get converted to mileage. Researchers at Purdue, working with General Motors, are planning to harvest all of that excess heat energy to give cars more power.
The Purdue team's research is currently working with an alloy, called skutterderite, which can withstand temperature extremes. It's used to build a thermoelectric generator, which produces a current when exposed to thermal differentials. These generators will harvest energy from exhaust gases, which can reach up to 1,300 degrees.
This process might pave the way for hybrids that charge their electric batteries during gas-powered runs, which can definitely increase their range and power.
[source: Popular Science]