Um, integrate hibernate?

Methane probably has more energy in it than gasoline. It has four high-energy hydrogen bonds while gasoline only has something like 2 per carbon, and the weight of a purely hydrogen and carbon hydrocarbon is pretty close to proportional to the number of carbons. Hydrogen gas has a LOT more energy in it than gasoline per unit mass. They used to power the Space Shuttle booster rockets with it before they switched to solid state fuels (Think plastic explosives). They might not have switched at all, except that they need oxygen to burn it with.