2003 Chevrolet Impala Owner's Manual - Page 314

Inflation - Tire Pressure The Tire-Loading Information label, which is on the inside of the trunk lid, shows the correct inflation pressures for your tires when they're cold. "Cold" means your vehicle has been sitting for at least three hours or driven no more than 1 mile (1.6 km). When to Check Check your tires once a month or more. Don't forget your compact spare tire. It should be at 60 psi (420 kPa). How to Cheek Use a good quality pocket-type gage to check tire pressure. You can't tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. Notice: Don't let anyone tell you that underinflation or overinflation is all right. It's not. If your tires don't have enough air (underinflation), you can get the following: Too much flexing Too much heat Tire overloading Bad wear Bad handling 0 Bad fuel economy If your tires have too much air (overinflation), you can get the following: 0 0 0 0 Unusual wear Bad handling Roughride Needless damage from road hazards 5-61