So I added extra oil. It's just below the 1 on the dip stick (picture for reference). My oil pressure on a cold start up sits about 20. I never really paid attention to where it sat before I lost pressure. So I took it around the block to see if it would go up under load, around 4k RPM I can get it to just about 40 PSI. When I got back and revved to about 4k again it would raise up to just about 40 again. So does that sound like just the o-ring to anyone? I also included a picture of how low the nose was on start up since it was suggested to have the front end lower...
My o-ring went bad around 170,000 miles, so if yours hasn't been replaced, it's probably time. When my oil pickup tube o-ring went bad, it was in December (cold). When the truck first started up, the oil pressure was VERY low. Once the oil warmed up and became thinner, the oil pressure seemed to increase closer to normal levels. It seems to kind of mimic your situation.
Think of it like trying to suck through a straw with a crack in it - it'll be easier to suck up water (warm, thinner oil) than it is a milkshake (cold, thick oil).
Side note in case it's relevant: I've run Mobil 1 5w-30 High Mileage synthetic oil since around 80,000 miles, and have always used a "good" oil filter (used to be Bosch, M1, or Wix, but for the last few years I've been using AC Delco since they are inexpensive and still seem to be highly regarded).
Hope this helps.
