re: I even drove almost 80 miles at redline and my engine is still working,I am very fortunate

Most who post on here about massive overheat have driven less than 5 miles in that condition. I would suspect your gauge is still not accurate.

You would be wise not to do this, and you really can't tell by the gauge the temps in the engine. You need to use a scanner or Ultra Gauge that reads from the OBDII pport under the dash. Some auto parts stores will plug in one of their fancy code scanners to demo or check codes, you could get a real coolant temp reading from that. Or back to Nigel's for a comparison with their scanner.

You are driving a Discovery 1? With a thermostat that is inside a metal housing held by two bolts?

 

Yes discovery 1 with housing. I have been shooting an infrared thermometer at the block in several locations. When my gauge reads 8 o'clock Im getting 179-210 readings. When I was redlining on the trip I thought the gauge was messed up again, but when I finally shot it I was getting 240-265 temps, and when I finally got home my coolint stated to boil out of the system. I plan on getting an ultra gauge as soon as I can though. But I every thing is working 100% at the moment, no high gauge reading and no high temps

 

mine was doing this, replaced t stat, wp, hoses, flush heater core, ended up having radiator rodded (only thing that made a difference I could see)and headgaskets

 

If you have a smart phone - look into a Bluetooth OBD reader and get the Torque app. You'll spend maybe $30 total and the features that the app has are great.