The recommended inflation pressures from the vehicle manufacturer should be listed in the owner's manual or on a decal in the glove box or door jamb in every vehicle. For most passenger cars, minivans and mini-pickups, the recommendations range from 27 to 32 psi. For full size pickup trucks and sport utility vehicles, the recommended inflation pressures tend to be about five to eight psi higher to reflect the larger tyre sizes and greater weight of these vehicles.
It is important to note that the pressures may differ for the front and rear tyres.
Adding a couple of extra pounds of pressure will decrease the rolling resistance of the tyres and make a slight improvement in fuel economy. On the other hand, it will also make the tyres harder which in turn may cause a rougher ride.
If you are carrying a lot of extra cargo, car pooling, hauling a lot of stuff in the back of a pickup or towing a trailer, a few extra pounds of pressure would be recommended to offset the added weight. Add the extra pounds to the rear tyres.
WARNING: Never exceed the maximum inflation pressure specified on the sidewall of the tyre. This number is the maximum pressure the tyre is designed to safely handle. Higher pressure increases the risk of tyre damage (when hitting a bump) or tyre failure.
Tyre pressure should be checked at least once a month and certainly before taking a long trip or driving at sustained highway speeds in case of a tyre leaks.