Does the thermostat in my BMW 5 indicate the correct values?

BMW driver question

I discovered in the on-board computer menu that my engine is not reaching the optimal temperature. I first replaced the main thermostat (Motorad), but it was still around 75-85°C.

After replacing the EGR thermostat, I get temperatures of 93-98°C on the road. Is this not too high? Most drivers report a range of 88-92°C. Can the EGR thermostat cause overheating? Should I replace the thermostat again?

The problem was on a BMW 5 E60 with a 145 kW M57 engine, but may occur on other models.

Response from BM Cars service

The main thermostat on the M57 engine has an opening temperature of 88°C. This does not mean that the fluid temperature cannot reach a higher value. At this temperature, a large coolant circuit is opened knocking down the engine for more efficient cooling.

During operation in summer temperatures, the coolant temperature can even reach around or slightly exceed 100°C. It is important then to use the right quality coolant, not water.

Overheating of the engine is signaled in this model by lighting up the check engine light and running the fan at maximum speed. A defective EGR thermostat can also lead to underheating or overheating of the engine.

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