The moral of the story with the factory gauge is to ignore or unplug it and get an actual gauge. I use an "Engine Gaurdian" thermocouple gauge on all my cars.
They read accurately even if water is lost - the standard type has to be immersed in water to read accurately, and even then you have NFI what the temperature actually is. Withthe thermocouple digital gauge you know down to the degree what the actual temperature is.
They have 2 programmable alarm levels. Let's face it - no-one watches their gauge all the time, and the first thing most people know about their car overheating is when they see or smell the steam. With the audible alarm you don't have to worry about it.