Re: Flucuating Engine Temperature
Chrome GT and nottyash,
Mine does the same; dial reads just over 70°C when on open road and reaches 90°C when in traffic. As advised by many on this forum I fitted a new stat and it made absolutely no difference. I checked the old stat by heating it in a pan of water and it started to open at 85°C. I'm think that the temperature gauge and transducer are very sensitive but incorrectly calibrated.
As long as your coolant temperature is always steady when on the open road, and steady in traffic, the gauge gets off the stop even in the coldest weather, and the engine never over-heats, then your thermostat is working, but the gauge may leave something to be desired. If the stat fails open (as they usually do) then your engine won't warm up. If it fails closed (which I've never seen) your engine will over-heat very quickly.