in my 80 240 when idling and after driving the oil pressure will drop down to 1.8-2.5 bar
as far as the manual sounds it looks like anything below 2.5 bar is bad.
whats yours like?

 

any questions I double check with a manual gauge to make sure the electric unit is correct. If my oil level drops the least bit below full my oil pressure drops some idleling. I like the metric system for it's simplicty but can't seem to chatch on to the bar thing.