Whats with all the paranoid threads lately with oil PSI like mentioned above the guage in truck is not all that accurate your numbers sound normal I get 23 PSI hot idle so your doing dam good!.
The paranoia comes from the issue progressing as mentioned by the OP and the oil pressure keeps dropping until it's 28 on the road and 8 at idle. Then you take it in to the dealer and he says, "Not really sure what's wrong with your 6.4 Hemi but you have metal shavings in the oil and we can fix the problem for $12k! This happened to me, just got it out of the shop and they said if I wanted to pay $4k they could tear the engine down and find out what happened. No noises, no drop in performance, just loss of oil pressure and engine is gone. This happened with only 120K miles on the engine. I'm 59, the truck isn't getting abused and gets the oil changed far sooner than required. I'm gun shy on the damn thing now, the very first engine was one of the improperly built 6.4 that hat the wrong wristpins. It lasted all of 5k Miles. So 8 year old truck with 125k miles and now on it's third engine.