Most temperature gauges form the vehicle manufacturers nowadays little are more than a fancy idiot light. They now are run by the computer and "normalized." This means they basically have three readings (1) cold, (2) "normal" and (3) Overheating. The computer monitors the temperature and as soon as the engine reaches a predetermined temperature threshold it quickly bring the gauge needle to the vertical "normal" position. As long as the temperature in is the "normal" range, the computer keeps it vertical. If the engine exceeds a predetermined high temperature, the computer quickly moves the needle to the "hot" position. This limits the usefulness of a temperature gauge, because as long as the temperature is in the "normal" range, the needle does not move.
Why did they do this? Because many people nowadays have more money (or credit) than brains. The manufacturers got tired of complaints from people when the temperature needle went to the top of the "normal" range when they were driving in stop and go city traffic, with the A/C full blast, and an outside temperature of 110 degrees. "What do you mean that's normal? I spend $70,000 for this vehicle and it shouldn't run hot, don't give me that BS, now fix it!"
So BMW, and others, went to normalizing the gauge to get rid of such unfounded complaints by people who don't understand engine cooling.
Last edited by Penguin; 11-04-2012 at 10:45 AM.