I never thought about MB oil pressure gauges' calibration, until now, that is. All I can think of is perhaps that by dropping from 2 bar (at idle) to 0 would be a near-full-scale deflection of the needle, and be easier to spot than a drop of a quarter of the useful range of a 8 or 10 bar scale.
I know this is a stretch, and also wonder if my car has a low oil pressure idiot light, to back up the gauge. I know, MB would say it's redundant, etc., but I'd be quicker to spot a red light coming on rather than a drop in a gauge (especially at night).
Robert W. Roe
1984 300SD 165,445 miles