i have a failed Smith's
oil temp gage, and an Autometer replica gage that was defective out of the box. I called Autometer about it, they did promptly send a replacement, and told me the mechanical gage's line and sensor was filled with Ether, to expand and cause the gage needle to work.
I was smarter the third time, as putting in a gage is a two hour job. Here is what i suggest to check your gage. Remove the sending unit, and put it in boiling water. Assuming you are at sea level, be sure it reads about 100 degrees C, or a bit less at some altitude. My first bad Autometer only got to about 60 degrees in boiling water.
It also depends on your sending unit location, when i had my sending unit in the
oil filter mount, it read higher than when i had it in my sump. My Aviad pan has a sump port of sending units. IN my Windsor at steady cruise, in "winter" it will read a bit below my 80C water temps (185 'stat), in summer it will read a bit higher. It will get hotter, up to 100 C max in hot stop and go.
I bypass my
oil cooler in the winter, in order to get my oil temps up to a reasonable temp. Too cool and it won't evaporate fuel and moisture, you should run about your engine temps to have your oil last the longest without contamination.
So, i suggest first checking your gage, easy to do. Let us know where your sending unit is, and if your cooler is hooked up or not.