HHO = A gas mix... 2 parts hydrogen and one part oxygen by volume
H20 - water
These devices are just portable electrolysis cells.. that do not separate the gas during production. Most scientific grade cells have the plates separate and can separate the gases.
HHO cells usually have the cells closer to improve production at lower voltages/amps... that makes the separation impossible...
Ether way.. with the way the gas is used.. it helps to make a complete burn of the petrol.
I am currently working on a 25 plate monster myself... every review of the HHO devices I have seen have yielded positive results...
Check this one out... this is my local station that tested one. There is a video on the right side.
http://www.wptv.com/news/local/story...13A28&gsa=true
Mine will dwarf this one in production (a coworker has purchased one and we tested output)