Turbo: It's usually not necessary, although it makes sense. At operating temperature is when the thermostat opens, but by that time you will have coolant overfow all over the place due to thermal expansion. Bring it up to operating temperature with the cap on, and check it again when it cools down. Mine started going after the middle line when I was synchronizing it. I was wondering where it should stabilize (between middle and high?). I shut it off because it felt pretty hot around there. Basically, until where is normal for the needle to go?