The big secret is that water (H2O) can be turned into a POWERFUL fuel (with a very similar formula, HHO) through an easy yet little known process...Here's their whole spiel, and you can listen to "Rachel the spokesmodel" tell you all about it.
It's so powerful that when it was first discovered the government (influenced by big oil companies) banned it because it was too effective.
This guy says it's not a scam:
I believe that some people are calling water for gas a scam because they expect more than a book. Visitors to the website more than likely quickly look at the pictures and expect a ready to go package to be delivered.But he could be working for them, right? Even if he isn't, what kind of cost-benefit are we looking at here? If it costs $500 to save $50, we are not doing very well...
This is not the case; the books provide pictures and part numbers and places to buy the items needed to build your own system and instructions on how to install it.
After doing some research on the basic part of the system I have found that it operates very similar to alcohol injection kits that have been available for racecars for many years.
Alcohol injection kits can be very expensive, costing up to $600. The water for gas website has found a less expensive way to build and install a system that will increase fuel economy
Please tell me where these claims are debunked in the comments.
Bottom Line: It's sometimes hard to tell the difference between brilliant and deceptive new ideas, but the truth will emerge eventually. (Relativity, anyone?)