I live in the Palm Springs, CA area where summer days are pushing 110F. My '95 E420 rarely breaks 90C even in stop and go driving with the AC in full array. I recently took 4 Marines with their luggage from the airport back to their base. It is a 65 mile trip starting up a long grade into the high desert. Even up this grade the car temp stayed a little over 90C then dropped back below 90C
There is a new thermostat, water wetter and less than a gallon of coolant, the balance water. I am one happy camper!
Anziani
'93 300CE 188K
'95 E420 122K