The users manual says to maintain your weatherstrips that you should use Weatherstrip Lubricant (GM Part #3634770) or Dielectric Silicone Grease (GM Part #12345579). I have heard that silicone should not be used on weatherstripping. The GM Lubricant is very-very expensive. What is the best to use? I see that others have suggested using 1Z Einszett Rubber Care Stick Gummi Pflege. Are there other sources/items that can be used. What has been your experience.