I personally installed a HHO unit in my Trailblazer and it works. I did the old school measuring for mpg because I dont have that option, I have trip counter and a calculator, So I used to be able to go 350 miles at best on a tank of gas, about 23.3 gallons of gas (to be accurate), Now after adding the unit I am averaging 400 to 420 miles per tank depending on the weather, I live in colorado and if anyone who has 4 wheel drive knows when you engage it eats up you gas mileage. Anyway, I also have a mixture I created that allows me to leave the water in when the temperature drops to 15 below 0. I like it, doesnt affect any of my warrantys its just an add on. So far the only maintenance was to add a little more water as it "breaks in" simple, and when the cost goes back to 4 bucks a gallon this thing will definately pay for itself. Thanks for your time.