When the thermostat opens (160 or 180) has nothing at all to do with causation of overheating.
In cold weather, with a 160 degree thermostat, you will likely suffer from cold feet on a short trip. If it is extremely cold out, your feet will be cold for the entire trip. Condensation in the oil will not be boiled off either. That is bad news.
A 160 degree thermostat opens at 160 degrees. It does not regulate the maximum temperature whatsoever after that point. The radiator/fan/coolant/water pump/waterjacket condition/timing/air-fuel mixture dictates the coolant temperature above the opening temperature of the thermostat.
