It is an electronic gauge, and operates within a "window" for standard temperature. Watch it, and you will see once it warms up it goes from "cold" to "half-way" pretty quickly and steadily. It will sit at half-way for a fairly large temperature range. I am not certain of the range, but for conversation let us say that anywhere from 160°-230° is normal. You could be running at 161° or 229° and the gauge would be in the exact same position..."half-way". Just because you did not boil over does not mean you were not operating above the intended coolant temperature, and if you would have waited another minute the high-temperature light would have come on and the gauge would have peaked.