As I said in the other thread, I recently bought a 2001 E-Class and I noticed that the trim looks almost like it is tarnished but since I didn't have it since it was new, I wouldn't know for sure. Does the trim tarnish and need to be cleaned like silverware? Here's a picture so you can see what I'm talking about.

 

Mine is headed in that direction too. What you showed was jet black when the car was new. Polishing will not help because the black pigment is no longer present. I asked one of the detail people at my dealer and she said the only cure is to replace the trim pieces. You might prevent it from getting worse by applying some wax, at least that's what I'm hoping for. Metal polish will only remove more of the original pigment.

 

I never would have guessed that was jet black when it was new.

I wonder how it would look if the pigment all comes off and if it would be silver...

 

From looking at the pieces on my e420 after I had to replace one that was damaged, I believe the vertical piece is black anodized aluminum with a clear coat. the UV in the sunlight bleaches out the anodizing, turning it the purple color you see. If they were anodized, the only solution is to replace the piece.

 

I don't know what color they ultimately fade into. I guess it would depend somewhat on what color your car is. If it's dark maybe not bad. Purple is the early stage. One guy posted photos of his trim and it looked like bronze to me.