What is it?
Proper tire inflation pressure is the specified air pressure given by a carmaker for a certain tire on a specific vehicle. This pressure specification should not be confused with a tire’s maximum pressure, which is usually listed on the tire’s sidewall. Some vehicles may specify different pressures for the front tires and the rear tires.
For the small amount of time it takes, checking tire inflation at least once a month is one of the best investments you can make to get the maximum life out of your tires. Proper inflation can also improve gas mileage by more than 3%, when maintained regularly. Keep this in mind: Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi (pounds per square inch) drop in pressure of all four tires. You may want to check your tires more often during the winter months. Tires will lose about 1 psi of pressure for every 10 degrees Fahrenheit of temperature drop.
Keep an accurate tire pressure gauge in your car’s glove box (many gauges at “air stations” give false pressure readings) and check the tire pressure when the tires are cold. Never trust the appearance of a tire as a gauge for inflation. A tire could be 10 psi low on pressure and not appear to be low on air. Use the recommended inflation pressure listed in your vehicle’s owner’s manual or on the inflation sticker found on the driver’s door jamb. While you’re at it, don’t forget to check the spare. There’s nothing more annoying than a flat spare when you have a flat tire.