Physicists disagree amongst themselves on issues.
That is true. However, you still can't generate energy from nothing. It takes more energy to split the water into hydrogen and oxygen through electrolysis than is generated from burning the hydrogen. You also have the fact that the alternator isn't 100% efficient.
So where does this energy that is the greater sum of its parts come from? There's no catalyst that is reducing the energy required to split the water molecules. The hydrogen doesn't dramatically increase the efficiency of the combustion of the gasoline.
The processes involved are well known, such things have been tried before without such results, and there is nothing new in this process to explain why the combination of it with a gasoline motor would suddenly become more efficient.
It's a scam.
I always believed that energy isn't created its converted, its the efficiency and the by-product of the conversion that matters.