The only official figure I know is Minumum 2 bar at 2000 rpm with oil at 80deg C ( maybe 85 can't remember)
80 deg C is quite hot, aftera good run, would take quite a while to get up there idling but if you wait until the fan has cut in a couple of times you should be getting close.
if you measure when colder the pressure will be higher.
you can't easily connect an oil pressure guage after a run as the oil squirts out but it is possible.
As you can see mine is out of spec at 2000 rpm, electric guages in cab may not be very accurate either ( pics of both guages taken at same time)
