Too Cool?

[Solina Dave]

Just curious. Does the engine on my '78 GL1000 have a minimum coolant temperature for optimal running. Or, in other words, can the engine be running too cool? One would think that the cooler the better, but I'm not sure. The photos are of my temperature gauge and also an operating sketch of the gauge. When I'm cruising, and the engine is at full operating temperature, the guage is reading exactly half way in the black section to the left of the 85ºc point. The fan operates "ON" and "OFF" about 2/3 of the way between the 85ºc point and the 110ºc point. All of that appears good, but I'm wondering if the indicator needle should be reading higher, possibly in the 90ºc range at cruising speed, or do you think the engine is running at an acceptable temperature?

Just wonderin'...........................Dave

[dingdong]

All engines are designed to operate most efficiently at an optimum temperature for proper fuel combustion. Your thermostat is designed to open at 180º F. So normal should be at or just above that. Actual temps naturally will vary depending on riding conditions. That said don't rely on that gauge for correct temps. 85º C is 185º F.

[Viking]

Further to Tom's answer, yes, an engine can run too cool. If it does not reach an appropriate operating temperature, your oil will not evaporate off the water and volatile contaminants, and will begin to form sludge. You would need an actual thermometer to verify what temps your engine is running at, as the sensor only sends a signal to a gauge, not an actual temperature. The sensor and the gauge may not be working together properly, and so you are showing a low scale. This could be a faulty sensor, a faulty signal, a faulty gauge, or a faulty thermostat, as, if the thermostat is stuck open, your engine will not reach its designed temperature.

[Solina Dave]

Thanks to both of you, Tom and Viking. That all makes sense. I was mainly interested in knowing if an engine might run too cool. The point about potential, and reasons for sludge build-up, is well taken.
i'm not so sure that I'm going to worry about it to any great degree. However, if I did want to explore it further, and I had an appropriate thermometer, where would I take the temperature, to obtain an accurate reading, while under normal riding conditions? Under idling conditions, without the benefit of the radiator, I would think that the engine temperature would eventually be higher, around the fan operating points?