Yeah, I've seen the "run on water" snake oil medicine.<quoted text>
I like where you are going-- except for the "run on water" bit.
That is pure BS-- sorry about that, but water simply has no useful energy to release, to run your car.
Unless you have invented an anti-matter converter? One that converts the mass of the water directly into energy? No?
Then "cars running on water" is not possible.
It's been a long time since Chemistry classes, but I seem to recall that breaking down the H2O compound takes a lot of energy. Pretty much you need something like solar or nuclear to make it commercially feasible.
But at that point, you'd better off desalinating ocean water for fresh water.