[david256]

My V8 does the same, Low Oil Pressure warning while sitting and after a lot of research I believe its the Volts/Alternator or gauges.

If you have a volt gauge watch the Volt gauge drop and at the same time the oil pressure drops, as my volts drop from 13.8/14 volts down to 12/12.5 volts the oil pressure drops. I suspect its either the gauges playing up or the Alternator is on its way out. Personally I think its the alternator as it plays up more when Im using the Air Con Fan on high and Head Lights.

btw I changed the Oil pressure switch/sender made no difference, so was just a waist of money.