What is the best thermostat

You need a 195°F thermostat and yes it matters. On a computer controlled engine the engine must reach operating temperature (195°F) within a certain amount of time from a cold start up. Usually within 10 minutes. This is so the computer control system can go into closed loop operation. If you have the wrong temperature thermostat in there the engine will not get to operating temperature, a trouble code will be set, and the service engine soon light or check engine light will come on. This will also effect your fuel economy since a cold engine runs rich until it gets warmed up. Hope that helps! Jim

Find a AC Delco oem part supplier , I've had problems with cheap thermostats from auto zoo and nipa .

Not much I can add to this except the stock rating was 197 degrees for the thermostat.