I have a 2012 c250 coupe with 79k kms. Recently I have noticed that the car temperature gauge takes a long time to reach the 80 to 90-degree mark. Also, it fluctuates up and down sometimes. The heater is running perfectly and takes about 5 minutes to reach an optimal temperature. No issues with the heater in sub-zero Canadian weather. I also have noticed that the car is running a bit rough, rpm fluctuating sometimes while in drive. I am not sure if this is a thermostat problem or the engine coolant temperature sensor problem or something else, coolant level is just a bit below minimum so will be topping that up.

thanks,

 

All I can offer is it appears you have excellent taste in small, fuel-efficient good looking coupes.

(Will cop to some bias here)

Please do keep us in the loop (about your rough running/thermostat issues.

ez