PITTSBURGH -- Avoiding jack rabbit starts and stops, keeping the trunk empty and checking tire pressure can all help drivers get better gas mileage. But there is one driving tip that will probably save more than all the others.

The Automobile Association of America (AAA) says slowing down may have the biggest impact on gas mileage.

But how much slower and how much can it save you?

Lou Ickes, of AAA, said, "That 10 mph difference could save you 15 percent of your fuel costs."

According to the AAA formula, drivers who drop from 65 to 55 mph and have a 12-gallon tank while gas is $3.50 a gallon can save as much as $4.50 per tank.

For drivers who fill up four times a month that's $18.

Two cars over the course of a year quickly brings the savings to $432.