Hi Bill;

High oil temp can be caused by a number of problems. I had the same issue with my 1978 C-172N. We checked the following:

Vernatherm valve
All engine baffling
Magneto timing
Oil cooler and lines
Temperature sending unit and wiring
Temperature gauge
Scat tube that routes cooling air thru oil cooler
Switch to Aeroshell multi-viscosity oil (20W-50)

And finally, the one that fixed the problem:

Installed the Cessna service kit to add a cooling lip
to the bottom of the cowling.

This all assumes that your engine is in good condition otherwise, as internal problems can also cause overheating, such as excessive blowby past the rings, bearing wear, etc.

Hope this helps.

Jon