believe it or not you want the engine to run hotter since it will perform better. Engineers specified that thermostat for a reason. The hotter the engine runs the most efficent in terms of combustion and fuel economy.

my 190E gets around 100c when its really hot out when im sitting at a light but on average day it runs steady at 90C when im crusin

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)