This is a really interesting topic for me, what with my '96 E300D (W210, OM606NA) at 275,000 miles and AFAIK the valve cover has never been off to even look at the chain. I suppose I should at least check the camshaft mark against the crank's OT mark to see if there is an "elongation" or other signs of wear on the chain and sprockets. I'd hate to have the chain break and ruin this near-perfect engine.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970