I take that with a grain of salt, just like all other fuel additive “mpg boosting money savers” out there. When it comes down to it, this electrolysis conversion doesn’t end up saving you. To create 1 joule of energy stored as H2 and O2 necessitates more than 1 joule of electricity. So you’re losing energy in the process of getting that electricity in the first place, no matter the process.

Something has to break down the water that becomes the fuel, which is another way of saying that now you’ve gotta fuel the process of fueling.