Despite historic high gas prices, Americans continue to travel the roads in record numbers. Follow these guidelines to have a little extra money in your pocket when you hit the road. Tires tie in to gas savings: You can save money at the pump simply by checking the air pressure in your tires regularly. The U.S. Department of Energy reports one pound of underinflation costs consumers two to three miles of gas per gallon. That wastes four million gallons of gas per day nationwide. Take time out of your busy schedule at least once a month to make sure your tire pressure matches the manufacturer's recommended amount found in your owner's manual. Tune in to tune ups: Keeping your engine properly tuned can save you big bucks. The U.S. Department of Energy says fixing a car that's noticeably out of tune can improve gas mileage by 4 percent. Healthy air filters: You should check and replace air filters regularly. Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent. Get the pedal off the metal: Fifty-five not only saves lives, it saves gas. Government figures show gas mileage decreases rapidly at speeds above 60 mph. Each 5 mph you drive over 60 mph is like paying an additional $0.15 per gallon for gas. Beat the heat: Buy gasoline when it's cooler outside, like early morning or later at night. That's because gas is denser in cool temperatures, and gas pumps measure by volume. You'll get more bang for your buck. Plan ahead: Cars hate gridlock as much as we do. Avoid congested areas in order to keep your car from idling. Drive sensibly: If you drive aggressively, by accelerating and braking abruptly, you're wasting fuel. By driving a little more sensibly, avoiding jackrabbit starts and stops, you can save yourself money by increasing gas mileage by up to 33 percent at highway speeds amd by 5 percent around town.