What worries me is that if the engine is running at a cooler temp than it should the ECT sensor will be putting in more fuel as it thinks the engine has just started and is still warming up. Secondly over here if you don't have an efficient heater in the winter it can be life threatening at -40C. The car will ice up on the inside BIG time then you cant drive then you freeze to death. Its like batteries, you dont have one that is iffy or on the blink, you get a new one or its curtains.