Just dirt for now damaging the paint, that can lead to rust later.It's just dirt, not rust, so all good.
Generally good advice but on our cars the painted parts under all 4 mudguards are plastic. Not a bad idea to clean once in a while but you don’t need to worry about the parts rusting. The mudguard screws are self tapping directly into plastic pieces without threaded metal inserts.Just dirt for now damaging the paint, that can lead to rust later.
Actually, the rear uses speed nutsGenerally good advice but on our cars the painted parts under all 4 mudguards are plastic. Not a bad idea to clean once in a while but you don’t need to worry about the parts rusting. The mudguard screws are self tapping directly into plastic pieces without threaded metal inserts.