What he said.
The thermostat determines the LOWER operating temp parameter.
Most thermostats are fully open 16°F AFTER their rating - 160°F=176°F, 180°F=196°F, & 195°F=211°F.
The fan-on temps programmed into the pcm determine the UPPER operating temp parameter.
Since the OEM program turns on the fans at 229°F & 234°F, the needle still gets close enough to the 'red' to warp exhaust gaskets, break exhaust bolts, and accelerate the dry rotting of vacuum hoses and plastic fittings underhood.
So if you have a 160°F thermostat and stock fan-on temps, your engine operates between 176°F & 235°F, instead of 195°F & 235°F with the OEM thermostat.
Long story, short - reprogram your fans; the sooner, the better.