If you learn one thing here, please learn that a thermostat that is operating as designed has NO ability to cause or help an engine run even 1 degree cooler in warm or hot conditions. Really. Learn that the thermostat has just two jobs and two abilities: 1) to help the engine warm up faster and 2) to help set a minimum operating temperature in cold conditions. If it's hot out the engine will run at the same temperature whether it's running a 165, 180, or a 195 degree thermostat. Really.
If you need an engine to run cooler in hot conditions look at the radiator, fan shroud, fan clutch or water pump.