2007 Cadillac 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. 9. Remove any rust or dirt from the wheel bolts, mounting surfaces, and spare wheel. 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. 426