GMC 1994 Yukon Owner's Manual page 309

You can operate some vehicles at reduced inflation pressures only when
you'll be carrying reduced loads. On those vehicles, the minimum cold
inflation pressures for a typical reduced load are printed on the "Improved
Ride Tire Pressure" label located on the driver's door. Weigh the vehicle to
find the load on each tire and see the label for the minimum cold inflation
Dressures for that load.
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:
Too much flexing
Too much heat
Tire overloading
Bad wear
Bad handling
Bad fuel economy.
If your tires have too much air (overinflation), you can get:
Unusual wear
Bad handling
Rough ride
Needless damage from road hazards.
When to Check
Check your tires once a month or more. Also, check the tire pressure
of
the
spare tire.
How to Check
Use a good quality pocket-type gage to check tire pressure. Simply looking
at the tires will not tell you the pressure, especially if you have radial tires
-
which may look properly inflated even if they're underinflated.
If your tires have valve caps, be sure to put them back on. They help prevent
leaks by keeping out dirt and moisture.
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