If it´s not running above a hundred (often), I´d leave the thermostat alone. The engine runs best. makes the most PS (or horsepower), and probably uses less gas, at right a round 90-100 deg celcius. I usually don´t worry, unless it goes above 105 deg celcius, then I watch closely.
The original thermostat opens at around 90 celsius. Motor was designed to run at around that temperature or slightly higher.
I´ve used a 80-85 degree celcius thermostat before, it really didn´t help much. It did help some, when driving with a trailer in the mountains.
I´ve learned that very slow or very fast driving, caused most of my high heat problems.
The temperature gauge, isn't always exact. Plus or minus 5 deg isn´t unusal.