I thought this was interesting. Everyone knows that when you see your temp gauge hit red in any stock automobile then that means it's basically overheated WAY over normal... not just a little bit. They manufacturers don't want people complaining that their car runs a little "hot" just because they interpret a high temperature as overheating. A car can run hot just fine without overheating. But if car makers installed accurate instruments then people would assume a high heat reading = car running too hot which isn't a problem.
So basically temp gauges in cars read in the absolute middle of the gauge until the engine becomes EXTREMELY hot. Then the gauge will peg to the red zone but by that time your engine has likely sustained some damage from the extreme heat. Here is a good tech article showing how to modify a Toyota pickup instrument cluster so that it gives you accurate readings and doesn't just display the middle reading and then SUPER HOT... like they do from the factory. To learn a little more about how this works just read this webpage discussing
how to modify Toyota temp guages.