cars are funny. my former 1989 300SE ran at just over 80C regardless of ambient. Lots more room in the engine bay than the C280.

My 95 C280 began to operate warmer after the first water pump change. design differences might make for variable temps compared to OEM pump.

Average out known running temps and go from there !

and keep cool !

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD