GMC 1994 Yukon Owner's Manual page 238

Remove all the wheel
nuts and take off the
flat tire.
1
Remove any rust or
dirt from the wheel
bolts, mounting
surfaces and spare
wheel. Place the spare
Rust or dirt on the wheel, or on the parts to which it is fastened,
can make the wheel nuts become loose after a time. The wheel
could come off and cause an accident. When you change a wheel,
remove any rust or dirt from the places where the wheel attaches
to the vehicle. In an emergency, you can use a cloth or a paper
towel to do this; but be sure to use a scraper or wire brush later,
if you need to, to get all the rust or dirt off.
I
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