MF35 Perkins Oil Pressure

How much pressure should these engines carry both cold and hot. Seller said that tractor had 15W40 oil in engine. I plan to change oil and filter but would like some guidance as to oil pressure before selecting grade.

Thanks in advance.

Dean

with straight 30W, oil pressure reads almost 80lbs at startup, after 2-3 hours of working the pressure will be down to 60 and at about 4 hours pressure will be under 60 sometimes 55 so I break for some chow and tall glass of iced tea

oil pressure was very slightly lower using 10-30, engine seems to use less oil with 30W but turns over real slow at -10F

please do not skimp on oil filter or oil changes

I have the two-coloured gauge on my '61 35 deluxe diesel. Cold, the pressure is close to the maximum on the green. After two hours of bush hogging or raking it is down about midway or a little below in warm weather with 15W40 oil. When I drop down to 400 rpm after extended running, though, the pressure can drop below the red line.

If anybody can put numbers and values on the colours, it would help.

BTW: the engine's oil consumption is negligible.