This page has a fairly complete listing of companies making
electrolysis cells for the add-on market for cars and trucks.
http://peswiki.com/index.php/Directory:Fuel_Efficiency_Hydrogen_Injection
I suspect that long-haul trucking is the biggest and most
demanding customer for these.
Here is one test showing a bona fide 30% highway gain for trucking
:
http://ihsresearch.com/gallery.php?id=3
This involved using a 1994 Detroit Diesel 60 Series Heavy Goods
Vehicle (HGV) at two different test sites near Winnipeg, Manitoba,
Canada.
Canada seems to have more makers of add-on systems than the USA
for whatever reasons. More long-haul trucking mileage per
population, for one thing. The cynic might say lax laws regarding
stock manipulation, is another factor.
Jones