Chevrolet 2006 Express Van Owner's Manual page 332

CAUTION:
{
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 needed, to get
all the rust or dirt off.
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7. Remove any rust or dirt
from the wheel bolts,
mounting surfaces
and spare wheel.
CAUTION:
{
Never use oil or grease on studs or nuts.
If you do, the nuts might come loose. Your
wheel could fall off, causing a serious
accident.
9. Lower the vehicle by turning the jack handle
counterclockwise. Lower the jack completely.
8. Put the wheel nuts
back on with the
rounded end of the
nuts toward the wheel.
Tighten each wheel
nut by hand until
the wheel is held
against the hub.