Gas prices up. So are scams.

NEW YORK (CNNMoney.com) – It costs less than $40 and, according to its Web site marketing, it will raise your vehicle’s fuel economy by 30 percent or more. Customers swear by it in testimonials.

Whatever it is, your best bet is to keep your credit card in your wallet.

Whenever gas prices spike, such product pitches spike as well, said Claudia Bourne Farrell, a spokeswoman for the Federal Trade Commission, the government agency responsible for investigating bogus marketing claims.

“More people than you’d probably think” get taken in by bogus claims of big fuel savings with simple devices, Bourne Farrell said.

CNN