How can I tell if a used car I bought still has a ceramic coating?

There is no simple home test that confirms a coating with certainty. Wash and decontaminate the car first, then look for consistent water beading or sheeting, an unusually slick feel and dirt that releases easily. Compare panels: an untreated area such as a recently repainted panel often behaves very differently. Service records, invoices or a sticker from the installer are more reliable than surface behavior. If in doubt, treat the paint as uncoated when deciding on maintenance and protection.