Your engine was designed to run right at 210 and is most efficient at that temperture. Ignore your friend's misguided recommendation to install a 180 degree thermostat, stick with the factory spec'd 195 degree thermostat. Installing a 165 or 180 degree themostat just makes the engine take longer to warm up to its designed-for 210 degrees. And since even the 195 degree thermostat is wide open at 210 degrees, installing a 165 or 180 degree thermostat will not make the engine run any cooler in normal conditions. The ONLY time a 165 or 180 degree thermostat would make it run cooler is in extremely cold climate conditions where that would not be a good idea since it would take a long time for the engine to warm up, likely causing a Check Engine light as well. The heater wouldn't work as well either.