I was seeing oil temps in the red, oil pressure ok but I still landed
immediately. Turns out the wire on the oil temp unit on top of the
engine (don't know what that is) was loose. Correct wrench to remove
the nut, washer and wire. Clean everything. Replace. Tighten correctly
(yes, an A&P was there - next door hangar). No more problem with
oil temps.

The easiest & cheapest fix I've ever had.