Whenever there’s a crisis, scam artists are quick to get into the act. With gasoline prices at record highs in the aftermath of hurricanes Katrina and Rita, bogus remedies have arrived right on time.

There are useful ways, of course, to cut down on gasoline consumption, including President Bush’s advice to drive less. But many of the claims that you can get huge mileage savings by using special oil and gas additives or devices are fraudulent. Some could actually damage your car’s engine or add to air pollution by increasing exhaust.

Here are some false claims to watch out for, according to the Boston office of the Better Business Bureau, which serves eastern Massachusetts, Maine and Vermont.

. “Improves your fuel economy by 20 percent.” The U.S. Environmental Protection Agency has tested more than 100 alleged gas-saving products and has never found a single one that improves mileage significantly. Among the offenders are “air bleed” and “vapor bleed” devices, “liquid injection,” “mixture enhancers,” and “internal engine modifications.”

. “I got an extra 4 miles per gallon with your product.” The bureau warns that few motorists have the ability or equipment necessary for precise measurement of gas mileage changes.

. “Approved by the Federal Government.” No federal agency has endorsed any gas-saving product.

On the positive side, the Better Business Bureau advises some driving habits that can, indeed, improve your gas mileage. First of all, choose only the lowest octane level that your car needs. The owner’s manual will tell you which is the right one. Higher levels will boost the cost by 10 or 20 cents per gallon.

Maintain your car properly. Keep the engine tuned and the tires correctly inflated and aligned. Change the oil and oil filters on time. The bureau says clogged filters can decease gas mileage by 10 percent. Drive more efficiently. Stay within posted speed limits; gas mileage drops rapidly at speeds over 60 miles an hour. Accelerate slowly from a dead stop, and avoid “jackrabbit starts and stops.” Use overdrive gears and cruise controls only as appropriate.

Keep windows closed when traveling at highway speeds. An open window creates a drag and can reduce gas mileage by 10 percent. Avoid dirt or gravel roads where possible. They can cut gas mileage by 30 percent. Get extra weight out of the car trunk. Carrying an extra 100 pounds can mean a 2 percent loss in gas mileage.

Products that promise better gas mileage may sound tempting, but maintaining your car and making simple changes to your driving habits will do more to save you dollars at the pump.