Ok, this might be a little long, but it is kicking my backside. Last Oct, my engine crankcase (IO-360-A3B6D) had a massive crack under #1 cyl near Waco. I was able to make it to Waco and land safely. My A&P/IA and I removed the engine and brought it home where it was disassembled. There was no metal found and oil pressure never dropped. The engine had under 500 SMOH. We obtained a yellow tagged case and reassembled the engine. It now starts right up and runs great. However, the oil temperature gauge (OEM analog) will slowly climb in the pattern past the red line (245f) and will slowly drop to just under redline on descent to land at low power settings. Shortly after landing I can hit the oil filter with a laser temp finder and it will read 185-190f. I added a second temp probe on the front of the engine with a digital gauge. It too will get up to 230 or so. I have since tried two different vernatherms, replaced the factory temp sensor and flushed out the oil cooler. The original vernatherm end looked great. I flushed out the vernatherm cavity and reached in and felt with my fingertip and could not detect any burrs or imperfections. I’m still not convinced if I actually have high oil temperature, or if the gauge has gone wonky. I’m at a loss what to try next.