You don’t need a new car for a water engine
You do not need a new car or a new engine to be able to run your car on water and use water 4 gas. If you want to have a water engine, you will simply use the old engine and fix a converter inside it. It is the converter that would turn the car into the water engine. Aside the converter, you do not have to do any modifications to the engine.
The converter is a very economical device. When you install this component, you will be able to recycle the hydrogen produced over and over again such that you will be running on less fuel. So you can have the constant supply of fuel from a single glass of water. This recyclability is the reason why hydrogen proves to be a very efficient fuel.