There may be a bit of confusion about what a thermostat does. A thermostat controls the minimum temperature of the coolant, not the maximum temperature. You will not prevent overheating by changing to a different thermostat temperature.
If the coolant runs at a lower minimum temperature it will cost fuel economy and power because more energy is wasted to the coolant.
I think the reason they used to recommend changing to a higher temperature thermostat in the winter was to make the heater work better.
However the system has to be sealed and pressurized to prevent coolant loss.
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