This is a press release from the Oregon Attorney General's Office:

Attorney General Hardy Myers today warned Oregonians of the increase in scams connected to the rise in gasoline prices and alerted them to three schemes being used to defraud customers.

“Twenty-first century con artists are using the Internet and headline news to follow trends and monitor catastrophic events for new opportunities to strike,” Myers explained. “As consumers are looking for a way to cope with the record price of gas, criminals are looking for a way to make a fast buck. We are asking all Oregonians to make themselves aware of these potential scams to protect themselves.”

• So-called “Gas Saving Products” are being marketed and sold everywhere, door-to-door, over the Internet, on the telephone, and even in multi-level plans. Our office has investigated the claims of gas-saving devices for decades and not one has been found to significantly improve gas mileage or reduce emissions. In fact, some devices have actually damaged car engines. Before purchasing any of these products including oil and gas additives, smart consumers check out the claims by calling the Attorney General’s consumer hotline (listed below) or visit the Environmental Protection Agency’s testing website at www.epa.gov/otaq/consumer.htm. For gas-saving tips that really work visit the Federal Trade Commission’s website at www.ftc.gov. 
• Owners of Recreational Vehicles (RVs) are warned about joining fly-by-night RV Gasoline Clubs. Scammers go door-to-door in campsites or RV Parks selling “exclusive” memberships in RV Gas Clubs. For several hundred dollars, buyers are promised huge reductions in gas prices wherever their club cards are accepted. Unfortunately, the phony club cards aren’t accepted by anyone and it is almost impossible to track down the itinerant sellers.
• Be watchful of signage in and around gasoline stations. Oregon law makes it unlawful to mislead customers with confusing signage about the price of gasoline. Make sure the prices seen on the large signs from the street or highway match the signs on the station and the pumps. By law the gasoline dealer must display the lowest price for all grades of gas and diesel fuel sold to the public. The dealer also must post the price for gas purchased with a credit or debit card if different from using cash. New pumps display the cash price and automatically change to the higher price charged for using a card just before the fuel is pumped into the tank. Consumers should double check the pump price as the fuel is being pumped. Also, make sure the pumps are calibrated in the same measurement used to offer prices. For example, ensure all information is given in gallons, not a mix of gallon and liter measurements. If you don’t understand the signs, ask what they mean and do not purchase gas until you understand what the transaction is going to cost.
• If you suspect a gasoline station is purposely confusing consumers about what they are paying for gasoline or failing to disclose added fees for credit card use, report them to the Attorney General by calling the Attorney General’s consumer hotline at (503) 378-4320 (Salem area only), (503) 229-5576 (Portland area only) or toll-free at 1-877-877-9392. Complaints can be filed online at www.doj.state.or.us by clicking on “file a consumer complaint.”