Jeepman 1320. Where are you getting your reading from. Is your sending unit at the filter? I get similar readings and I am getting the readings at that location. I have very little clearance (around a quarter inch or less) between the exhaust manifold and nipple coming out of the block that the sending unit attaches to. My idle runs about the same as yours and pressure readings get below 20psi when hot at idle. I am running 10w30 now last summer 20w50 without a big change. I am going to try to get the sending unit fitting farther away from the exhaust. My assumption is the I am heating the oil before it gets to the sending unit. It stays hot because that is a dead end so there is no circulation. When you rev the engine it counter acts or does it's job and shows a pressure increase. Also I am going to bump my idle up closer to 750 rpm (makes sense).