I've also never successfully cured an idle overheating issue with a colder thermostat. It's actually backwards. With a thermostat set to open at 160, the coolant temperature at idle will never dip below 160 therefore the thermostat will never hold the coolant in the radiator for a long enough time to allow it to cool down in the radiator, the coolant just flows through, yes it cools down but it would cool better if it got to hang out in the radiator a bit longer to dissipate the heat. My best bet is to always strive for the factory recommended thermostat of 190-195. That ensures the thermostat does it's necessary cycle to allow the coolant to stay in the radiator and properly cool down the engine. Yes it will run hotter but these engines run a heck of a lot cleaner and meaner around 200 degrees. Reducing the carbon buildup in the combustion chambers. With a 160 and insufficient low speed airflow you almost always get that constant rise in temperature as the car sits idling. Where as with a higher set thermostat and proper airflow you get a consistent temperature. I know it goes against a lot of what we have learned but I have had my fair share of overheating battles down here in south Texas and since I've adopted that philosophy I achieve the target temperature every time. Electric fans are a last resort. usually only added if the electrical system has been updated/upgraded and if the car has an A/C system so that additional airflow is necessary to keep everything happy. Otherwise I stick to 7 blade 17 inch fans, HD clutch and shrouds.
