If you look up the product, it is some type of hydrocarbon that you mix 1:200 with your fuel. The exact nature of this miraculous product and the way it works is not stated. Clearly it won't work and these (and a multitude of other fuel-saving products) have been debunked many times.
There are devices sold which, when installed in the intake/fuel system, are supposed to increase power and also improve fuel mileage by (insert your own outrageous percentage). That would be a neat trick, except that they don't work, and probably would have the opposite effect. Since these are a "one-off" scam, the purchase price is high.
What scammers are really looking for are products that you must use regularly, and fuel fits into that category. There was a classic case a few years ago in Australia involving a solid hydrocarbon fuel additive and those with time on their hands can read about it in the following link:
http://en.wikipedia.org/wiki/Firepower_International
Note that we do have scientific and technical expertise in this country, but very little testing of the product was ever carried out before $millions were wasted. If I recall, the magic pill was something like Naphthalene, the compound used in moth-balls. For more entertaining reading, search for "Energy Polariser".
The only fuel saving device that actually works is "green" tyres; about 2 MPG.
Fuel saving products often have a grain of scientific credibility, such as the water electrolysis equipment; obviously the small amount of hydrogen generated is not going to do anything by itself, but it is impled that the hydrogen helps the rest of the fuel combust more efficiently due to an unspecified effect.
Human health scams such as homeopathy are similarly enticing because they seem to be related to the established science of immunisation. Here again, the vanishingly small (sometimes vanishing completely!) active ingredients are claimed to have magical effects on the water in the preparation.