'Gas-Saving' Additives Only Subtract From Your Wallet

And yet people continue falling victim to these scams.

"I see desperation from folks who are trying to figure out a way to deal with energy costs as high as they are," Dixon said.

The EPA has evaluated or tested more than 100 devices promoted as gas-saving and has not found any that significantly improves mileage, said Howard Schwartz, director of communications for the Better Business Bureau of Connecticut, which also issued a warning to consumers.

"People are being inundated with these ads that appeal to their frustration about high fuel costs," Schwartz said. "But these products will simply help empty your pockets with questionable technology."

Energy and Environmental Analysis, a consulting firm in Arlington, estimates that 99 percent of aftermarket products do not change fuel economy, according to Schwartz.

Before you buy one of these devices or products, consider these warnings from the FTC and the BBB:

· If a company claims it has an endorsement from the government, that's a big, fat lie. The EPA has issued reports based on its testing and evaluation of some products. There's a set of links to those reports at http://www.epa.gov/oms/consumer/reports.htm. By the way, if a company claims that its product has been evaluated by the EPA, ask for a copy of the report.

· Be leery of customer testimonials. Come on now. How can you really know whether the people praising a product aren't actors? As Dixon points out, few people have the ability or the equipment to test for precise changes in gas mileage.

· Be skeptical that a single product can achieve double-digit improvements in your fuel economy.