gasoline has a massive amount of energy, like 50KJ/mole - as it is now, mainstream automotive technology harnesses 10-15KJ/mole of that energy as kinetic force. the rest is heat and chemical conversion.

Imagine that, for every $40 tank of gas you buy, you actually only use 8$ of it driving.

of course there are methods of harnessing more of that energy but they are pricey and why bother when we poor chums will take the garbage they sell now...