A few days ago, I learned about another emerging technology to improve gas miileage in most vehicles. It's called a Pre-Ignition Catalytic Converter (PICC). They moved the catalytic converter from the exhaust system to the fuel line. The thought is that you should fully break down (vaporize) the gas molecules before they enter the engine, so all of it burns, instead of breaking down the unburnt fuel that the engine has already wasted. When you combine this with a hydroxy booster on the air intake, carbon monoxide is almost completely eliminated from the exhaust. Some smaller cars get over 100 miles per gallon with this installed.
I found a link to another car mod which allows it to run on pure tap water. Until I see it, I'm very skeptical. This conversion was done on a beater Camaro with a stock 350. It's pretty intriguing how instead of using a pulse width modulator (PWM) to regulate the electrolysis, he just uses 60Hz from an off-the shelf 110v AC inverter and opens and closes relays using the spark plug wires. I believe that since he's not using any hydrocarbons, the real fuel is the nitrogen in the air. The hydroxy created by cracking the water only catalyzes the reaction. The NOx emissions must be enormous, but since he's feeding the exhaust back through his water reservoir as sort of a bubbler, I presume that a lot of the NO2 and NO3 is dissolved back into the water. Then, in the electrolysis process, is it breaking the N2 and O2 apart, so it can be burned again? Since it uses a second battery, wouldn't it be smart to add a second alternator?