Reason number 2385 to fire all the American Car company execs. Dave from the RE program decided to enhance his car's fuel efficiency and lower his emissions. Dave is not an auto mechanic, although he is mechanically adept. He bought a Hydrolyzer kit on the internet, and improved his mileage by 15%.
How it works:
The car's electricity is used to run a small current through distilled water and electrolyte, potassium hydroxide. (I know! Big words for this blog, but stay with me, I don't understand 'em either). The water (H2O in metric) is charged up, and this splits the hydrogen and the oxygen into hydroxy gas. This is then funneled into the intake manifold. The car's oxygen sensor knows that enhanced amounts of oxygen are present, and lowers the amount of fuel burned in the mixture. The oxygen and hydrogen are burned hotter than plain air mix, so the car burns the fuels more completely and cleanly.
That's it. The hydrolyzer doesn't run while the car is off, so you aren't dealing with stored hydrogen. The device has a bubbler unit that passes the gas to the intake manifold. This also prevents a potential backfire from getting to the source hydroxy and causing an issue like an explosion.
No it's not some form of free energy, but the small amount of electricity used up is easily made up for by the fuel in the hydrogen and clean burning of the oxygen. I've seen it and it actually works.