I've been watching developments in the field of hydrogen fuel cells that supposedly bring higher fuel mileage to gasoline and diesel-powered vehicles for some time now. The most aggressively marketed of these is one called The Hydro 4000:
After watching that video last month in California, I started looking at other places on the web, to see if others were actually testing Hydro 4000s and getting similar results. Some are, and others are not. A cab driver in Massachusetts named Elliot has been testing a hydro 4000 on his taxi for about a month now. Initially, you could sign up for his e-mail updates, but the day before yesterday, he started posting them online. Here's a link to his updates.
Another company pushing the conversion of hydrogen to boost motor fuel efficiency is Water 4 Gas. They have a slick site, with youtubes and lots of testimonials, like:
I've got a 1969 Landrover Series 2a 2.25L Diesel. I put magnets on the fuel line and increased the mileage on a set 17 mile route at a steady 40mph to 27.87mpg. I then constructed the single cell system and fitted it. My first run was with the bubbler closed and on the set run increased my mileage to 28.84mpg. A positive start, but I felt that the engine was being starved of HHO. I then reduced the length of the two feed pipes going to the closest point on the air intake manifold to 4 feet each from five feet and opened up the bubbler to allow a moderate amount of air through. I then ran the same run (each run took 35 minutes) and compared the results. My 39 year old Landrover did 71.43mpg!!!!
If these gizmos actually work - basically doubling fuel efficiency, then we need to start seriously making usable products readily available. Combined with implementing anti-speculation legislation, use of fuel-saving modifications on a huge level, would initially have great benefits. Coupled with a longer range decrease in demand for motor fuels, it could all combine to lessen demand on fuel, further driving the price of fuel back down to sane levels.
If you start looking into HHO modifications and other "water for fuel" ideas, you'll see a lot of skepticism, mostly based on the second law of thermodynamics, and the reality that you're just not going to get something for nothing.
I remain fairly skeptical, but I'm still looking, and doing some modest research.