A strange on going issue. I have a 292 that I rebuilt several years ago. It runs great, but every year when the temperature drops, my oil pressure goes nuts. When cold ,when fired up, a steady 50lbs. As it starts to warm and I start to drive, the mechanical guage ( 4th one) will start to slam up to 80-100 psi. When it gets up to temp, it settles down to a steady 40-55 lbs. I run 10-30 oil, and have checked the relief valve in the gear type pump. This has gone on for years and have never blown out a filter or anything, but it does have me scratching my head at this time of year.( temp in the 40s). Hmmm

Sorry, I didn't take that to mean that you were on the fourth gauge. For some reason, I thought that you were trying to point out which gauge you were looking at within the cluster. Silly, I know. Anyway, does the oil pump pressure relief valve move smoothly within its bore? I'm wondering if it is just tight enough to cause drag until it is warmed up.