Cadillac 2011 STS Owner's Manual page 462

The vehicle may have either aluminum or
chrome-plated wheels.
Keep the wheels clean using a soft clean cloth with mild
soap and water. Rinse with clean water. After rinsing
thoroughly, dry with a soft clean towel. A wax may then
be applied.
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The surface of these wheels is similar to the painted
surface of the vehicle. Do not use strong soaps,
chemicals, abrasive polishes, abrasive cleaners,
cleaners with acid, or abrasive cleaning brushes on
them because they could damage the surface. Do not
use chrome polish on aluminum wheels.
Use chrome polish only on chrome-plated wheels, but
avoid any painted surface of the wheel, and buff off
immediately after application.