If your
oil temperature sending unit is easy to get to, why not just get a cheap gauge at NAPA or some auto supply store and check it at the sending unit with the gauge. I did that for both my temperature and pressure gauges on my old Cobra when I wanted to see if the gauges in the dash were reading about the same. In my case I also got a new sending unit as I wanted to compare it with the readings the old ones were giving.
Ron