Another way to get the most from your Gas is to create a vapor chamber heated by the exhaust of the engine. If you convert gas into a vapor it is fully burned inside the engine.
On carbureted engines, you can get extreme fuel mileage by turning the fuel from a liquid to a vapor before it goes into the engine. One man created spinning fan blades in the bottom of a carb that would vaporize the fuel as it hit the spinning blades from the carb. It mixed the fuel better, which made for much better combustion of the fuel.

Vaporizing water, and injecting it in the form of steam into the mix as it goes into the carb also creates higher combustion. It is already a vapor therefore it is pretty much ready to burn when mixed with the gas vapor. That works on the same principle as Nitrus Oxide injection.