My '81 SD runs at about 95-98 in summer traffic with AC on. Doesn't concern me until it goes over 100.

The '81 SD aux fan only comes on with the AC. You might want to check that the radiator fan is OK.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer