1, weak oil, use some Lucas oil stabilizer on your next oil change, I'd go with 1 quart.
2. weak oil pump.
3. worn bearings will rob oil pressure due to the increased gap, if your engine has high mileage this may be the case.
If check gauges is lit and the oil press gauge is low, you have low oil pressure or a failed oil pressure sending unit.If check gauges is lit and the oil press gauge is low, you have low oil pressure or a failed oil pressure sending unit.
Defective gauge, defective oil pressure sending unit, low of oil, defective oil pump.
mechanical
Low oil pressure or a defective oil pressure sending unit.Low oil pressure or a defective oil pressure sending unit.
1999 Chevy table oil pressure gauge low and check gauges flickering
A mechanical oil gauge may bounce if you are low on oil. An electric oil gauge may bounce if the sending unit or the gauge itself is faulty and of course you are low on oil.
Oil level and oil pressure are different. You don't need to have full oil to get normal pressure.
It could cause a high reading on the gauge.
Low oil, no oil pressure, bad sending unit, wiring, bad gauge,.............
There is a low oil pressure light.
Your dipstick is the obvious sign. ( I trust you know about the dipstick .) Your oil pressure gauge is another warning--low oil pressure can be caused by not enough oil.
Low oil level, low engine rpm, low oil pressure, failed oil pressure sensor.