Do mothballs in your tank improve gas mileage?

That's one of the many gasoline additives and devices some people claim will save you money.

The Federal Trade Commission has tested more than 100 of these and found the ones that worked only provided a marginal improvement.

George Nitta, host of the local "Automotive 101" radio show, swears by mothballs and even shows on his Web site how to stuff them into gas tanks. He said the older mothball type made of napthalene helps raise octane levels and thus mileage. "I get six to eight miles per gallon more," says Nitta, who drives a Chevrolet truck powered by a 350 cubic-inch Corvette engine.

The mothball idea has been around for years and even has been examined by the Discovery Channel's Mythbusters (they found it plausible) and National Public Radio's Car Talk ("The only thing that Jim will guarantee is that if you put mothballs in your gas tank, any sweaters you store in there will come out without moth holes").

Others are dubious about the mothball mileage claims and suggest it might harm engines.

Nitta also recommends using BG 44K fuel additive now and then to help clean up and improve mileage from engines with fuel injectors.

Reach Greg Wiles at gwiles@honoluluadvertiser.com.