Since you said your mechanic measured 80 psi, I think your gauge may not be incorrect. While this may be in-spec, I know of no other MB that runs that high. I may be concerned that there is a blockage down line of the oil pressure sending unit. Thus causing the high pressure. This may have the effect of not providing enough oil to the rest of the engine.
Anybody elses thoughts on this?
'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)