As a matter of fact the temperature gauge is irrelevant since E38, E39, E45 and E53 models. It will stay in the blue when engine is cold, move to the middle at 120F or so and start moving to the red over 240F. Once it starts to move to the left the engine is toast. This is how I overheated my first 528i and this is how millions of owners overheated their modern BMWs. In my E30 the needle will move visually with every 4-5 degree change of the coolant temp and I can figure out early if there is a problem of some kind. The only modern BMW with a real gauge is the E46 M3 which acts similar to the old school ones.