I can’t believe this hoax is still around. The first time I saw it was in 1938 as a seven year old reading my father’s Popular Science magazine. The chemical world is not like the social one. In the physical world you CAN"T get something for nothing. Or as the Second Law of Thermodynamics says (paraphrased) -You can’t win, and in fact, you can’t even break even. Almost every way you convert energy from one form to another, say chemical to mechanical through combustion in an engine cylinder you lose part of the energy as heat.
Water, whether it’s expressed as HHO or H2O, and whether it’s solid, liquid or gaseous, in this case is really part of the ashes when gasoline (a mixture of hydrocarbons) reacts (burns) with the oxygen in air. Carbon dioxide is the other part of the ashes. The energy is all gone. To convert the water back to hydrogen and oxygen takes a great deal of energy - even more than you can get back by burning them together again to power an engine.
I wish more people has stayed awake in their high school physics and chemistry classes (or their teachers were better) so they understood the meaning of the laws of thermodynamics.
It’s like a very active thread on another forum where someone heard about a car that would run on compressed air and thought this was a wonderful way to avoid using gasoline. The first thing you need is a compressor with a motor or engine that requires a lot of energy to compress the air. As soon as you do that, the air gets very hot. As the heat dissapates from the storage tank, there goes a lot of the energy you put in to pressurize the air. And to go even a few miles to the store, you’d need a tank truck to hold the amount of compressed air to run a piston or turbine engine.
And now, off of my soapbox.