So I'm about to pull my hair out trying to figure out truck. So my truck is a 2009 chevy 3500hd 6.0. oil pressure has always seemed kinda low since we bought truck. Shows 286k miles but unsure of engine is original. Used to be around 12psi at idle. If the truck was at idle for a extended amount of time the lifters would start clacking. Replaced oil pickup tube oring and didn't change much. After that didn't change much I replaced oil pump, oil pickup tube and oring, and pressure relief valve in oil pan. Oil pressure sits at about 17psi at idle now which I suspect will drop even lower when the oil gets older. Replaced oil pump with a high volume pump. Any ideas? Or is this a normal oil pressure for these trucks?