Yeah anything over 210F while driving would be a concern. I always do a preflight check on all my vehicles & yep on the D2’s I use my scangauge II to monitor the temps, but 172-210F is my temp range. I’ve bought LR’s and driven them home and the darn temps were like 205-229F...... I of coarse swapped out the thermostat & fan clutch. Then I was back in my normal temp range with zero damage. It’s the constant 215-235F zone that spells disaster!

 

How do you guys measure your temps?

 

UltraGuage, plugs into OBD2.
A temperature gun can be helpful too.