P21sis my standard arsenal of wheel cleaning. This does a fabulous job at cleaning the wheels on routine washes and is effective even when I slip up and let a few weeks go by between washes. For caked-on brake dust, I'll switch to the P21s gel and follow-up with the normal P21s Wheel Cleaner spray on a second round. The painted and polished Mercedes wheels look brilliant and never have any coating or oxidation issues as compared to Sonax Full Effect.