What simple, often-overlooked maintenance check can improve your gas mileage up to 3% and be critical to your driving safety? In this case, it really is a lot of hot air!
Your car's tires can't hold the car up by themselves. They're not that strong. You can collapse the sidewalls of a tire by standing on them, and you weigh a lot less than your car does. The real job of supporting the weight of your car is done by the pressurized air in the tires.
If your tires are underinflated (i.e. the air pressure is too low) then you could be losing up to 3% of your gas mileage. Even worse, underinflation is the largest cause of tire failure, so your safety could also be at risk if your tire pressure is too low. Underinflated tires also tend to wear out faster and they can cause your car to handle poorly.
Even if your tires maintain their air pressure, you need to check that pressure regularly. Changes in the outdoor temperature can cause your tire pressure to change. A 10 degree Fahrenheit change in the outdoor temperature will cause your tire pressure to change by about one pound per square inch. As the thermometer drops in the fall and early winter, your tire pressure drops along with it and your tires will soon be below optimal pressure.
Get a good tire pressure gauge and check your tire pressure at least monthly. Check them when the tires are cold, not after you've driven the car for a long distance. The correct pressure for your tires should be in your owner's manual. If you don't find it there, open the driver's door and look for a sticker on the door jamb or on the back metal panel of the door. If you can't find the correct tire pressure, ask your car dealer. Don't go by the pressures listed on the tire sidewall -- those are usually average safe ratings for the tires and may not be optimum for your car. You may find that the recommended pressures for your front and rear tires are different. Make sure that all four tires are properly inflated for best gas mileage and safety.
Remember to check your tire pressure with an accurate tire gauge at least monthly. Overinflation can also be a problem because it can make your tires wear quickly and unevenly and it may make your car handle poorly. Keep your tires at the pressures your car's manufacturer recommends for best tire life and gas mileage.