It just seems to me that using the water supply to run cars for everyone in the world who drives is a bad idea. Our drinkable water supply would last what? A month maybe? We do need vehicles that run on something other than gas, but engines require oil to work properly. Switching from gas to another fuel will work, but we are going to have to develop engines that don't require any form of oil before we can stop being dependent on it.

As long as we have rain our drinking water is safe. We will have more rain when the transformation to a hydrogen based society is finished.
Water is a byproduct of hydrogen combustion. When hydrogen burns, it leaves only water vapor (also possibly some trace compounds from the inevitable combustion of lubricating oil, plus a tiny amount of oxides of nitrogen. As for the oil they are working on ways to make engine oil out of vegetables. it is very possible. there is just one catch presently.
In cold climates it gets very thick and loses its ability to flow. there are chemicals that will keep it closer to a liquid state but they in turn add more pollution then conventional motor oil. So they are still working on that one.
The major problem is getting out of the DEATH GRIP that big oil has on all of us. there is so many ways but most people wont do them because it might inconvenience them.