I'd wonder if anyone has changed the oil and not used the right oil. Usually it's the oil that will stretch the chain more than the load, especially in colder climates. I doubt if any oil change places, who are always promoting changing as much as they can, are using the exact right oil.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)