For all the decent engines i've seen, both 5.9 and 5.2, cold start idle should be anywhere from 40-60 same while driving. I've never gone above 3krpm while cold so I don't know what that would be. When its warm, it really depends on the state of your engine. Anywhere from 30-60 is just fine for warmed up operation. If its dropping to 20 or below at idle, you have a problem. Likely a main bearing is getting loose and its time for a rebuild. Or there is the off chance someone put WAY too thin an oil in for the temperature its operating in. Like a really thin winter weight oil used in the northern states and canada when you're down in texas might do it. Keyword, might. Usually low oil pressure is due to one of three things. Bad oil pump, worn bearings, or contaminated/oil past its service life.
