Get yourself an infrared temp pistol about 50 bucks. Point it at the boss on the intake manifold where the temp sender is to get the real temp, then look at your temp gauge to see where it's at.
And never question the accuracy of that toy ?
Infrared light is estimating the heat coming off the surface. The fan can effect what it sees. Ambient lighting, daylight, florescent light, etc.. will too. Anyway, The water temperature below can be significantly hotter.
Look at it this way, infrared can see a man running around in the dark but if you want to know if he has a fever, you'll need to stick a thermometer in him.
