For the past two months I have been studying the various websites pushing hydrogen kits for gas and diesel -- and there are thousands. I am now to the point where I want to hear from someone who has actually done it! My ole' 96 PSD has 178K on it, and nothing I have done so far has helped the towing mileage, including chipping, a 4" pipe, and an AirHog. I don't want to hear about the impossibility of hydrogen helping to improve mileage, or about how the H2 doesn't help diesels. I want to hear from those who have done it and it either helped, or it didn't help, and the kind of unit used -- including distilled, tap water, or KOH, the amperage, and voltage used.