What weight oil are you running? That sounds a lot like you're running some sort of water-thin multi-viscosity oil that flows through the system faster than the oil pump can compensate for at low speed. 500 crankshaft RPM means the oil pump is only turning 250 at idle. That's barely above cranking speed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!