My '86 300E had 210,000 miles on it when I sold it, it now has had a valve job and all is well 250,000 with no new chain. The tensioner is such that it ratchets into place to take up slack. The chains are short and don't wear that much. I'd leave it be.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS