It's a great question. Can you run your car on water? A lot of websites and stories online and on the media are claiming that possibility. However, the best answer to the question is, "... sort of."
You can not run your car on water alone. Please do not try it. However, it is possible to run your car on a mixture of gas and water and get amazing mileage. But please do not rush out and dump water in your tank. It's not quite that easy. You're going to need some more equipment.
So, how does this work anyway? Well, it works on the principles of the hydrogen generator. You see, your car's engine runs great on gasoline, and it runs even better on the right mixture of gasoline and hydrogen. You remember hydrogen, the Hindenburg was filled with it when it blew into smithereens. Probably because of that disaster, we do not typically fuel things with Hydrogen these days. But, if you had a way to safely introduce just a little hydrogen into your car's fuel / air mixture, your mileage would go nuts and your engine would burn cleaner than it ever has before.
This works because Hydrogen is extremely volatile and it burns extremely clean. So, just a little bit of it increases the efficiency of every little combustion in the internal combustion engine under the hood of your car. Because the gas burns more efficiently you do not need as much of it to get the same amount of power out of your engine. Therefore you end up buying less gas.
But, you have to get that hydrogen from somewhere. With some major advances in hydrogen technology, brilliant scientists have developed a hydrogen generator that will fit under the hood of almost any car. It joins onto your car's fuel system and all it needs to work is a little bit of water that you supply and some electricity from your car's battery.
The hydrogen generator itself works on the principle of electrolysis. With electrolysis, when two pieces of metal are put in water and given an electrical charge, the resulting force causes the water to separate it's hydrogen atoms and oxygen atoms. Those atoms mix together into a gas called HHO or Oxyhydrogen. The output of the hydrogen generator, the HHO gas, is sent through the car's air filter and into the piston chambers where it mixes with the gasoline and causes that gas to burn much more efficiently and cleanly. When it's all said and done, you spend less money on gas. Some people can even double their mileage by introducing a hydrogen generator under the hood.
You may be wondering how much this is going to cost. Well, like most things in life, the price varies a great deal based on what you want to do. There are do it yourself kits available as well as full on installations. You can even purchase guides that will show you exactly how to build your own system from parts readily available at your local hardware store. So, it just depends on what you want to do.