George from detailedimage.com has it right on the nose:

From Todd Cooperider's guide on detailing an m3:

http://www.detailedimage.com/Ask-a-P...grey-metallic/

"Basically any leather, rubber, or vinyl can be treated with Prestine Clean, so here I’d like to show you a few other areas that you can use it.

Here you can see that the door seals are dry and discolored."



"Simply spray some Prestine Clean onto a microfiber towel, and then wipe down the seals. Now they’re cleaned and conditioned, and will help to keep the cabin sealed up properly."