Proper air pressure makes tires wear evenly, prevents tire failure and increases handling and traction. While air pressure is responsible for the great task of supporting the weight of your vehicle, it is an easy aspect of your vehicle to maintain.
Inflation pressure is affected by changes in temperature. Because of this, the most critical times to check your pressure are in the fall and early winter months. For every ten degree Fahrenheit decrease in temperature, your tire's inflation pressure will decrease by approximately one psi (pound per square inch). Similarly, a ten degree increase will cause a pressure increase of one psi.
Since tires generally lose about one psi per month, it is important to check them regularly and often. You should be able to find the recommended tire pressure for your vehicle in the owner's manual or on your tire information sticker. Keep in mind that the tire pressure listed is a "cold" pressure. This means it should be checked in the morning before the car has been driven. Also, remember if you check your pressure inside an attached or heated garage, you will lose pressure when you enter the colder air outside the garage. Add 1 psi for every ten degree difference in advance to account for the temperature change.