Wait, a synthetic filter is +20 psi over a conventional? Heck, I didn't even know they made "synthetic" filters. That's the snake oil I've been looking for my truck!
Last summer I was getting the check gauges light and gauge was negative on my '99 NBS 4.3 Vortec. I had about 5 psi with mechanical guage, so I switched to something like 5W-50 or 10W-50, and got a slight boost. It now has about 8 psi at idle checked with a mechanical gauge. Dash shows about "0" psi.
These are all idle pressure. It does go up as RPM increases. By buddy keeps arguing with me saying to change the oil pump, but I keep telling him it's the bearing clearances. I'm at 266K miles, so the truck owes me nothing. Recently, I developed an engine oil pan leak, so I will drop the pan to take a look....not really sure what to look for
Oil pickup tube o ring is the only thing I can think of. Engine "seems" to run fine.
I'm getting ready to retire the truck from being a daily driver, so not sure if I should just do another junkyard 4.3 or do an 5.3 swap, also from junkyard. Rebuilding the original engine with machine shop rates is going to be too much money. The transmission needs a valve body rebuild too, LOL.