Cadillac 2007 DTS Owner's Manual page 426

CAUTION:
{
Rust or dirt on the wheel, or on the parts
to which it is fastened, can make the
wheel nuts become loose after 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.
426
10. Place the spare tire on the wheel-mounting
surface.
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. Remove any rust or
dirt from the wheel
bolts, mounting
surfaces, and
spare wheel.