Canton claims 215 is to have condensation evaporate out of the
oil.
I tend to believe this theory:
https://www.offshoreonly.com/forums/...temp-chart.jpg
And here is a thermostat that can do that:
High-Flow Engine Oil Cooler Thermostat, 185F FSM-185
There are many others out there.
Yours rock solid at 215, shows the thermostat AND cooler are working well, just a bit high for me.