Always use an accurate tire pressure gauge to determine your tire pressure. Pressure gauges are available at your Toyo tire dealer or auto parts store. If you must drive over a mile for air, measure and record the underinflation amount of each tire. Upon arriving at the service station, measure each tire's inflation again and if the pressure has increased, adjust the amount of additional air pressure needed. For example, if cold pressure should be 35PSI, cold pressure was 28PSI, and current pressure is 33PSI, you should inflate the warm tires to 40PSI and recheck them again when cold.
Tires lose pressure naturally through the process of permeation.
Changes in outdoor temperature can affect the rate at which tires lose air. This change is more pronounced in hot weather. Generally speaking, a tire will lose one or two pounds of air pressure per month in cool weather or even more in hot weather. Remember, underinflation is the leading cause of tire failure, so check inflation pressure regularly. It is normal for pressures to build up as a result of driving.