GMC 2009 Savana Van Owner's Manual page 330

CAUTION:
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Rust or dirt on a wheel, or on the parts to which
it is fastened, can make wheel nuts become loose
after time. The wheel could come off and cause an
accident. When changing a wheel, remove any rust
or dirt from places where the wheel attaches to the
vehicle. In an emergency, use a cloth or a paper
towel to do this; but be sure to use a scraper or wire
brush later, if needed, to get all the rust or dirt off.
See Changing a Flat Tire on page 5-80.
5-88
CAUTION:
{
Never use oil or grease on bolts or nuts because
the nuts might come loose. The vehicle's wheel
could fall off, causing a crash.
8. Remove any rust or dirt
from the wheel bolts,
mounting surfaces
and spare wheel.