I traded my 02 X5 for a new X5 last week. After washing it for the first time today I discovered a problem I haven't had with my previous X5 or current 04 530. The black running boards, wheel trim and lower bumpers were very hard to clean. There are dried dirt spots on them and I haven't been able to get them out. When I pick up my cars from the dealer they always have tons of oil on the wheels that splashes. Would that have anything to do with it? Thanks in advance for any help.