Time it takes: 7 minutesAbout half of car owners don't test the air pressure on their car tires often enough, according to the Rubber Manufacturers Association. The recommendation: Do it once a month or before any long trip. The payoff: Properly inflated tires improve your fuel economy by 3.3%. You can buy a pencil tire gauge for less than $10. Check the pressure when your tires are cold. If they need air, head to a gas station within a mile of home.