Because of the way the oil reacts with the heat and the oil viscosity changes. it is a normal occurance and the specs you state sound perfectly normal for an idling engine. the oil pump and oil regulator valve are controling the pressure and as the oil heats up it gets thinner and hence the lower oil pressure. pressure goes from high at start(cold) to lower at operating temp. (ever notice that cold oil pours slower and appears thicker than hot engine oil) you can not just add thicker oil because during start up it must flow to lubricate everything, as a lot of engine wear occurs at start up.
Obviously depends on RPMs. Normally 15-20psi at idle. Could be as high as 30-40psi when the engine is under high RPMs.
if i remember correctly when you first crank the engine the oil pressure should be around 60psi. after it warms up about 40psi.
40psi
40psi
40psi40psi
Oil pressure varies but should normally be around 40psi
it is 40psi
40psi plus or minus 5
14",15",16"...........35psi min 40psi max 17", 18", 19" ............40psi min 51psi max
16 lbs.
35-40psi
40psi +/- 5