Here is a comment from a guy who installed a HHO generator on his Diesel.
This came from one of the many “naysayer blogs” where these guys are so smart it makes you want to vomit, with the many scientific theories they throw around. None of these “brain children” have ever tried installing an HHO Generator on anything.
Junk? LOL. I have a 2007 GMC Sierra with the Dmax. I have been researching HHO for only a few weeks when I decided to get a system. Let me tell you it was the best thing I ever did. Before I was getting 27mpg on highway 65mph. Now I am getting 42mpg. I know seems like BS. I’m telling you it’s not. It’s a gas that is much more powerful than diesel and gasoline. What is so far fetched that a gas makes this power and increase in mileage? Nitrous is a gas and it makes tremendous power when added. So why can’t HHO increase the performance? From what I have researched, HHO gives better performance out of diesels than it does gas engines. I would try it if I were you. I got mine from ebay for $200 and is by far the best mod I have got for it. Better than the tuner, exhaust, intake combined. I am curious to see what kind of hp gains it gives. It definitely is quieter has smoother shifts, and better acceleration. I recommend to all to try it. Took me 15 min to install.