Even if you have a Tire Pressure Monitoring System (TPMS), as equipped on many newer vehicles, you should check your tire pressures regularly, at least monthly.
Most tires lose one pound per square inch (psi) of air per month, assuming the temperature does not fluctuate much. If temperatures drop, tire pressures also drop. Every 10 degrees Fahrenheit (°F) drop in temperature causes tires to lose 1-2 psi.
Underinflated tires increase friction against the pavement and can cause excess tire wear, even blowouts, when the vehicle is fully loaded or overloaded. According to the National Highway Traffic and Safety Administration, 1 in 4 vehicles have at least one tire that is significantly underinflated.
Find the correct tire pressure specification for your vehicle on the tire placard on the door jamb -- the inflation pressures stamped on the tires may not be correct for the vehicle.
You cannot tell the appropriate tire pressure by just looking at the sidewall of the tires and estimating how flat it looks against the pavement. Tires have various sidewall flex characteristics based on their aspect ratio (section height divided by width), traction rating (e.g., A, B, C) and intended use, so use a quality tire gauge to check your tire pressure against specifications.
Temperature is a factor when checking tire pressure. Your vehicle's recommended tire pressure is its cold tire inflation pressure. Check it in the morning before you drive more than a few miles, or before rising ambient temperatures or the sun's radiant heat affect it.
According to the US Department of Energy, keeping your tires inflated to the proper pressure can improve gas mileage, "Under-inflated tires can lower gas mileage by about 0.2% for every 1 psi drop in the average pressure of all tires. Properly inflated tires are safer and last longer."
Staying on top of vehicle maintenance will give you more trouble-free miles and peace of mind. Stay informed with a Chilton subscription.