[Renoir White]

The thermostat opens when the coolant reaches near operating temperature when it can then be allowed to flow to the radiator to be cooled and then begin the cycle again.
Yes you are right ... in the olden days (sigh) motorist use to fit a summer thermostat and a winter thermostat. The winter one would be a higher degree C rating so the engine would get hotter and warm up faster before the coolant got around to the radiator. In the summer this temperature was too high so a lower degree C thermostat had to be fitted to match the higher air temperatures which reduced the cooling effect of the radiator.

 

[BradleyW]

Makes sense, cheers.

I've done some digging. My previous thermostat was 83c. The new one is 89c. Is this an issue?

On ECP and GSF, the 89c stats come up for my vehicle. The one I got off eBay (which warped) was 83c.

 

[Renoir White]

No its not an issue. In my opinion the 89 is a better suited one. 83 seems rather low unless you are somewhere tropical.