Oil Pressure

[Wizard52]

Any ideas on what oil pressure range should be in the 4.2 TDi
I have VDO gauge and on start up cold it shows 60psi and when cruising at 100kph is stays at or close to 60psi. Obviously it drops when revs drop.
When coming back from Temora airshow via the hilly New England highway, as water temp got up to 100c and a bit more, (normally 85 to 90) oil pressure dropped well below 50psi even at higher revs. Oil is cooled by water so it is logical oil temps would increase as water temps rise.
Using Fuchs 15 40 oil Truck+ so happy with it.
So question is what is normal pressure and how much should it drop at higher temps.

[PeeBee]

I dont have the numbers you seek however would question the accuracy of the gauge. The viscosity is related to temp and pressure is simply system resistance, so if the oil is hotter/thinner it will flow more readily that when cold. I find my Chev diesel starts up cold with maybe 50psi, then at temp running at 100kphr its sitting at 22psi and at idle hot, maybe 15psi. This isnt an indicator of wear just the parameters above and viscosity can be altered by age of oil and service life as well.