Depending on ambient air temps and how hard the engine is working, the oil thermostat may not even open. The difference in temperature you are feeling on the oil cooler may be due to heat transmitted up the pipe from the engine or from air circulation.

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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