Actually, the pressure running is determined by the opening pressure of
the relief valve in the oil filter housing. Normally around 65 psi,
but some are much lower (the Volvo TD spec is 30 psi at 2000 rpm --
gear pump on the front of the crank).
Flow is the key -- I remember being told that some high powered Italian
sports cars had big warnings in the manual about not exceeding 2000 rpm
until the oil pressure came down as the engine warmed up -- back in the
60's, the oil was so stiff with the engine cold the valve train was
starved of oil until the viscosity dropped as the oil heated up. Hight
rpm cold meant a new cam and lifters!
Peter
