Total Cost (including installation) is from $200 or less. 
The typical product from a competitor will cost you $1200 plus $400 to install, so the break-even point is months as compared to days.
Oh and I particularly like this item: Discover IRS refunds owed to you by law for using green technology in your vehicle! Well, that goes for all of them. Just wanted to point that out to you. But then, maybe you should not disturb those buggers, you know?
Water4Gas is NOT the Author's invention. And it's not new. Based on old "forgotten" US Patents they have developed devices that use a little electricity out of your car/truck battery, to separate water into a gas called "HHO" (2 parts Hydrogen + 1 Oxygen). HHO, also called Brown's Gas, Water-Fuel or Hydroxy, burns beautifully and provides TONS of energy - while the end product is just WATER! Mobile Magazine says: HHO provides the atomic power of Hydrogen, while maintaining the chemical stability of water.
Hands down the Water4Gas site that I will send you to contains the clearest and most compelling information around the use of Water to produce Hydrogen (or HHO) on demand and help improve Gas Mileage, reduce emissions, steam clean the engine every day, improve engine perfomance, even in trucks, and much much more. The other sites don't even come close. OK, I take that back, the second one is just as clear, maybe clearer, at least to non-techs.
I am just astounded! Too bad my car died a few months ago. Well, when I get a new one, or a used one, believe me! I will buy this product/kit and the info from the Water4Gas site.
When you join these folks you become part of a society of voluntary experimenters and even get access to their Engineers. You will not find this with other outfits. And that's one reason why this Guide is a bit more expensive than the others. But... you may not care about the extra benefits. If so, go with the #2 of the TOP 3, below.
This group holds on patents, so you can go ahead and even manufacture and sell your own kits. Be an Entrepreneur!
Finally, when you become a member you will have access (telephone numbers and so on) to all of their suppliers. You will also learn from 100s of drivers from around the world, if you wish. For more info click on the link below.