This was possibly my solution: https://www.improvedracing.com/high-flow-engine-transmission-oil-cooler-thermostat.htmlas I have found the original bypass is not available from MB and will need to be sourced from a so equipped engine. Also the original is a pressure valve not a tempurature valve. The external temp valve would offer more precise control of oil temp if that matters but maybe it does not need that precise control.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT