On Tue, 30 Jan 2007 19:01:12 +0000 (UTC), David Scheidt
wrote:

The people that sell these things make specific claims: "Better fuel
economy!", "More power!", "Reduced emissions", etc. Fuel economy,
power production, and tailpipe emissions are all testable by widely
known, well understood, and generally agreed to be useful and valid
methods. Fuel magnets are not a new idea; people have been selling
them for 50 years or more. If they worked, you'd know about it,
because engine manufacturors would include them in their product.
Once one vendor did, everyone else would have to follow suit -- all
things being equal, would you use the engine that is rated for 10%
more fuel use?

All good points. In addition the US government would surely have
discovered these magical powers by now and specified them for use on
the extensive fleet of military diesels. This has not happened.

Meanwhile, the people who have shelled out their hard earned cash for
these gadgets have an emotional commitment to believing that they
spent the money wisely. It's the placebo effect.