Before you get excited about the notion of dramatically improving your fuel economy with the latest fuel saving device, keep one thing in mind... Of all the investigative reports done by shows like Dateline NBC, and numerous magazines like Car and Driver, Popular Mechanics, Consumer Reports, most of the gadgets that make claims of improving fuel economy that were installed and professionally tested provided no increase in fuel economy.
Gadgets that promise better fuel economy are not new to the market either. The United states EPA has been testing these devices now for over 35 years. You can download product evaluation documents from the EPA that date all the way back to 1970.
For as long as there have been engines, there have been folks trying to make them run better. Gasoline engines are inherently inefficient, so many believe there is room for improvement either through fuel additives or mechanical adjustment. While it's possible to make engines slightly more efficient, it's usually done through design and not modification. That means my Chevrolet Tahoe will always get roughly 14 MPG., and by design, a 1986 Chevy Sprint will triple that rating with an average of around 49 MPG.
Every time fuel prices go way up, people peddling gas saving devices come out of the woodwork. Everything from magnets that you clamp on your fuel line to prevent the molecules from clumping together to voltage conditioners that claim to "smooth" out the electrical current to your vehicles computer so it can adjust fuel trim more efficiently.
The device which has the biggest following is the hydrogen gas generator. These are usually sold in kit form over the internet. They mainly consist of a handful of amateurish looking items like a mason jar, some plastic aquarium tubing, wires, clamps, cheap-o vacuum T's and the like. These are usually advertised with language like "run your car on water."
It's certainly true that you can make highly combustible hydrogen gas from water, so, the claims are partly true. If you use enough energy to break the hydrogen and oxygen bonds in water you get gasses like oxygen which support combustion and is a necessary part of regular combustion. You also get twice the hydrogen gas which is highly combustible and can be used as a fuel. Breaking the hydrogen and oxygen bonds using electrical energy is called electrolysis. Adding some DC current to water gets the whole process started. It's very easy to do, so, it is no wonder the concept has a cult-like following. Using suitable electrodes made from non corrosive materials and a little electrolyte like baking soda or lemon juice added to regular tap water to make it slightly conductive, you can make as much of the stuff as you can afford to. It's very magical to those who slept through basic chemistry.
While hydrogen may be a storage fuel choice for the future, there isn't much hope for the average weekend mechanic -- or -- professional for that matter, to attach a hydrogen generator to a vehicle and produce the amount of hydrogen gas required to make it useful as an aftermarket upgrade. The best production of hydrogen utilizing the vehicle battery and charging system would only produce about 1/1000th the amount of gas volume needed to power the vehicle.
Please, do not be a victim! Do your homework and look at both sides of the story before shelling out your hard earned cash for something that's likely to only add insult to the injury of record high gas prices.