Quote:
Originally Posted by sailorboy1
doesn't make sense to me that the oil pressure goes UP with reducing rpms
I've gone through 2 oil pressure and temp gages the last 8 years
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Oil pressure can go up slowly as you reduce rpms ONCE OIL IS HOT as at say 2000 rpm your
engine is producing ( for the sake of the argument only) twice as much heat as at 1000rpm. As the oil gets hotter it gets thinner & flows more easily thru the bearing clearances. Pressure is just resistance to flow. Then when you let it run at lower rpms the
engine will slowly cool down & oil viscosity will increase which will make the pressure rise
In our engine oil pressure 40 psi @ 1000 rpm cold & 15 psi @ 1000 rpm hot but if we let it run after it's hot at 1000 rpm for 10 mins unloaded it will climb back to 30psi this is running 15w-40
diesel oil. Oil temp after running 2+ hrs under full load is only 59oC & pressure is about 20psi. Engine is raw water-cooled
single.
But, I happen to know one of our main bearings has 4 thou clearance instead of 2 thou because some idiot took a little too much off when machining bearing i.d. Ask me how I know.

That explains partially our below spec oil pressure
It is likely the OP's problem is related to oil temp but if his
coolant temp is ok it's a little strange