The fact is it will not happen at all. There is an old, but true, saying: You can't get blood from a turnip! The Laws of Thermodynamics tell us that there is a tax on converting energy to useful work. That is; not all the energy in a gallon of gas can be converted to work. Not all energy contained in a ton of coal can be converted to electrical power. It takes a certain amount of energy to move a car of a certain size and weight down the road. I suspect that the thermal efficiency of the current gasoline engine is near its limit. Use of supercharging will likely help some. There is no way that the distance a car travels on a gallon of gas can be doubled. What Obama and his clones don't tell you is that there is an additional source of energy, batteries or possibly fuel cells. But the energy provided by either of these sources is free. In the case of batteries they must be charged by energy produced by burning coal, gas, or oil. In the case of fuel cells it is provided by hydrogen which does not occur naturally and requires energy to produce, that energy likely produced by burning coal, gas, or oil. So lying about getting more miles per gallon of gas does not change the truth no matter how often it is chanted by Obama and by the faithful.