Mercedes-Benz Gleitpaste (Sliding Paste)? That's the only compound used for sliding roofs that I know of. You can be sure though that you need to use what they specify for the roof. Can't use anything else I'm afraid. Too many stories of people thinking they can use alternatives with unfavorable results.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)