GMC 2009 Savana - Manual (Page 330)

{ CAUTION:
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.
8. Remove any rust or dirt
from the wheel bolts,
mounting surfaces
and spare wheel.
{ 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.
5-88