Problem is, water is made by cars with catalytic converters. They take the exhaust gases and convert some of the biproducts into water. Check out exhaust pipes; you'll see water dripping out every so often. We've been making water vapor for years. When I was a kid, I was told that there's the same amount of water on earth now that there was when it was made. Not that way now.
The byproducts of combustion are CO2 and H2O. Combusting gasoline creates CO2 and H20.
This isn't a bad thing, they ARE telling us there is a shortage of fresh water.
New building construction is being encouraged to use waterless urinals and composting toilets in commercial buildings. I kid you not!