Dave Plowman wrote:

Bosch engine management does this on lots of makes. The gauge isn't
showing true coolant temperature at all. Stays exactly on 'the mark' over
a wide range of normal coolant temps. Ideal for those who can't understand
the true coolant temperature can vary due to driving conditions.
A BMW I had allowed you to read true engine temp via the OBC display - if
you knew how to do it.

Mine has reduced the coolant temperature from a gauge on the prior car
(no doubt controlled by the computer rather than a direct read of a
thermocouple) to 8 LEDs, which very quickly reaches the 90°C mark.

Hidden on an 'extra' page of the trip computer is an oil temperature
gauge which takes much longer to reach 90°C, I thought oil would have a
lower specific heat capacity than water, so heat up quicker? Or is the
circulation of oil within the engine that much lower?