Ford Cargo Oil Pressure?

I have noticed recently that the oil pressure on my 'D' reg 813 (hoirsebox) drops a couple of notches on the gauge when i have been travelling about an hour or so, i checked the levels prior to departure and on return and there does not seem to be a problem water ok as well, could anybody suggest a reason for this, could i be using the wrong grade oil?
Bob, April 2011


done
old motor this,you haven`t said what mileage it has covered but it may just be an engine showing its age and wear

cdc, April 2011
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