HHO according to Wikipedia

When you google "HHO Wikipedia" the results list this page in Wikipedia. The article's title is Oxyhydrogen rather than HHO, which is rightly so because Oxyhydrogen is the more accurate name for HHO. Per the Wikipedia entry,

"Oxyhydrogen is a mixture of hydrogen (H₂) and oxygen (O₂) gases, typically in a 2:1 molar ratio, the same proportion as water. This gaseous mixture is used for torches for the processing of refractory materials."

It goes on to describe the production -

"A pure stoichiometric mixture is most easily obtained by water electrolysis, which uses an electric current to dissociate the water molecules:

electrolysis: 2 H₂O → 2 H₂ + O₂

combustion: 2 H₂ + O₂ → 2 H₂O

The energy required to generate the oxyhydrogen always exceeds the energy released by combusting it."

Among the listed applications is of course automotive -

"Oxyhydrogen is often mentioned in conjunction with devices that claim to increase automotive engine efficiency."

Interestingly enough, automotive applications warrant full separate discussions.

You can read the Wikipedia entry on HHO as hydrogen fuel enhancement here.

You can read the Wikipedia entry on water-fuelled cars here.