This is a transcript of BMW technical bulletin S.I. B 51 53 02 from September 2006
This Service Information Bulletin supersedes S.I. B 51 53 02 dated October 2002
Subject
Discoloration of Shadowline Trim
Model
E34, E46, E60, E61, E64, E65, E66, E83, E53 Equipped with Shadowline exterior trim
Situation
The optional glossy black Shadowline exterior trim may become discolored.
Cause
Analysis has determined that the discoloration is due to a film deposited on the trim which distorts the light reflecting off the trim. These deposits may come from car washes, hard water, or other environmental conditions.
Correction
Deposits that cause the discoloration can easily be removed by polishing with a quality swirl removing polish, such as Meguiars #9.
Note: The glossy black trim pieces are anodized, not painted, and the discoloration does not mean that the surface has been damaged. Therefore, the trim pieces should not be replaced for this complaint.