My emission tests here in Mass was better than if I dint have the hydrogen. the by products are water and Oxygen only good for emissions. Our state likes cars that use hydrogen its cleaner. You should go to the sites that have this and get some info. Don't listen to the types that still think the Wright Brothers never Flew. This Hydrogen works it burns hotter than Gasoline. so you have to not go over board and hurt your valves. Ive done the research. Go you tube and see demonstrations of Hydrogen burning from a canning jar with water and baking soda. When I first saw that i was sceptical until I did the same experiment, Then i made one for my car.. And its all history now for 3.5 years. Burns cleaner than any factory car that uses just gas..