as dell said,
I had a tired old 4 banger jeep engine that ran fine, but had low oil pressure at idle.
old dude at the napa store told me to run 50 weight Valvoline racing oil in the old jeep.
was not hard to start and it kept the oil pressure up in the 20+ range when engine was warm and at idle.
engine ran for many years with Valvoline racing oil, that is great oil.
they use it in tight new hot rod engines, so its not like you think of, when you think high viscosity gear oil.
might be worth a try, all it would cost you is an oil change.
also, you might add one qt of lucas oil stabilizer to the current oil, if you are running 30 weight oil, I used that in my old ferguson for years.
but I have had better luck with shell rotella 15w40 diesel oil, diesel oil still has zinc in it to protect the bearings, I also add a qt of lucas oil stabilizer to the oil.
most all other oils: they have taken the zinc out of the oil (your epa at work).