I have a 61'235 in my truck with a mechanical temp gauge, and in 70 degree weather I drove 2 miles up hill then 2 miles back and about 5 minutes after I parked the truck the temp read at operating temp for a little while before dropping. I think that it takes a while to register the temp and those old 235's take a while to heat up. Overall I trust my mechanical gauge to let me know I'm too hot, but also follow your nose! like a certain toucan once said. You will smell it getting hot about the same time your gauge reads hot in my experience.
