Cooler is not necessarily better. Mercedes designs there cars to run at a certain temperature for a reason. If they wanted the car to run at 80C and cooler, they would have put an 80C or cooler thermostat in the car.

On my car, whenever it starts running at 82C or less, I change the thermostat.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record