I have a G-Class with additional equipment “Stainless Steel Package” and am quite surprised that many small points are formed with corrosion spots on the spare wheel cover. After I carried out the “magnet test” I found that the spare wheel cover – in contrast to the running boards – is strongly magnetic. The vehicle is year 2012. The workshop was also quite surprised about the stains and replaced the cover free of charge. It is important to look at your “stainless steel” reserverad covers and let the cover at Mercedes-Benz be replaced free of charge. PS: The surface becomes more sensitive and reacts even faster from the constant overpolishing. I have the assumption that the installed “Edelstah” reserveraddications are not high-quality stainless steel and inferior quality has been installed. In my view, an improbable thei with such expensive vehicles!