I fitted a new thermostat to mine on Monday. The new thermostat was marked 92-107 degrees C and the gauge now hovers around 90 degrees (with an ambient temperature of 13 degrees). I assume that the temperature sender, being mounted in the coolant bridge, sees a lower temperature than the thermostat does.
The thermostat has two disc valves. The larger one is normally closed and controls the flow to the radiator. A smaller one looks as though it shuts off the flow in a small port behind the water pump. Presumably the larger disc starts to open at 92 degrees and then the smaller disc shuts the other port at 107 degrees.
Perhaps someone with TIS can confirm that the engine is intended to operate at between 92 & 107 degrees?
To reduce emissions I think engines are designed to run hotter than they used to a generation ago but it is rather uncomfortable for those of us worrying about overheating