Start with a good washing and clay them. If no avail, try something slightly acidic as degreasers tend to be basic, something like diluted vinegar, but do not let it dry. Most aggressive is to compound/polish if it's etched into the finish, be warned though some wheel paint tends to be very thin.
This video from The Rag Company may help. It's for water spots from hard water, but it's applicable cause hard water tends to be slightly on the basic side (higher than a pH of 7)