When it comes to gas-saving gizmos, it's like religion--you're either a
believer or you're not. And like religion, belief is based on faith,
not evidence. Magnetic fuel-line devices for boosting gas milage have
been around for decades, as have other gizmos claimed to improve MPG
(e.g., using fuel-line heating, fuel-line cooling, ionization, etc.).
The EPA has tested more than 100 gas-saving devices--under controlled
conditions--and hasn't found a single one, including four magnet types
like the one under discussion, that measures up to its claims.

For more info, take a look at a fact sheet recently published by the
Federal Trade Commission on gas-saving devices at
www.ftc.gov/bcp/conline/pubs/autos/gasave.htm. Consumer Reports has
also looked at gas-saving add-ons and found them wanting.

Believe if you want, but these things are pure snake oil. And they
don't all fall into the "well, at least it's not hurting anything and
it might help" category. Some, like additives that get dumped into the
fuel or oil, can damage the car.

Extraordinary claims, as Carl Sagan said, require extraordinary
evidence. It's ain't there.