Low oil pressure light coming on

An effect of low oil level may damage valve lifters, they may have experienced excessive wear.
Definitively, continuous running of motor with low pressure might damage the motor.
If you check always oil level and it is an ocasional event, as long as the engine wasn't starving for oil under load (i.e. the oil pressure warning light did not come on), it won't have suffered immediate, catastrophic damage
I would worry more about the cumulative effect of chronic neglect. After the car is fully warmed up and warning light come on at idle your engine is on its last legs.

Your oil light is not a level indicator, it is a pressure indicator. If your oil light is on with the engine running, it either means that you have a bad pressure sender or you have no oil pressure. I suggest installing a mechanical pressure gauge to verify if you do or do not have oil pressure. If with the mechanical gauge you do prove to have oil pressure then simply change your oil sending unit. But if you do not have oil pressure with the mechanical gauge, then you must drop the oil pan and find out why you have no pressure.

500 rpm when not in gear seems a bit low but not ridiculous. Oil light comes on when oil pressure is too low. Is your oil very old, do you fail to change it ever. Or your idle speed just isn't high enough to maintain pressure. You may need a new oil pump.

this means a mechanical gauge test is required to check actual pressure warm idling if low below 20 psi then the oil pressure pump relief is stuck open or engine bearing are worn

blew something in lower end --oil pump damaged --no oil or low level --check oil pressure then do compression test as well --since knocking noise is usually called rod knock

Hi. This issue has several causes, but the oil light indicator is a strong sign of low pressure in the engine. This will cause the engine lubrication rate to drop, thus, producing a illuminated oil light, and erratic Oil pressure readings. The necessary actions are to have a manual oil pressure test ran on this engine, asap. When running a manual oil pressure test, you will discover if the true oil pressure is low, or normal. If the test proves that the oil pressure is, indeed, low, this will confirm that the Oil pump is suspect.

Now, if the true readings given during the manual oil pressure test are indicating that the pressure is normal, this will be the result of a failed sending unit(oil pressure switch). Although the oil pressure is suspect, this is not your only issue here. There seems to be a abnormal compression rate, present. This is causing the rough idle, and erratic RPMs. I recommend to administer a engine block compression test, as well. This test will discover if , indeed, there are issues within the cylinder heads, and block structure, such as a worn head gasket, cylinder wall issues, and cracked block. Normally, these issue will send signs, like white, or gray smoke out the tail pipe, or discolored oil. It will, also, promote erratic RPM ratings, and a rough idle. Have the oil pressure test, and engine block compression test ran, asap.

Once the test are administered, you will be able to isolate the actual problem areas, more accurately. Check the spark plug wire sets, and ignition assembly for faults, also.

could be a malfunction of the oil pressure switch or u have not change the oil in time for some time and is sludged inside yuor engine, oil gets muddy (burn) it looks like is oil in it but is not

Several issues could exist:
Faulty light - get computer code reading no code good chance its a light/short
Oil pump low pressure test with external pressure meter
Oil pressure sending unit

Once you determine you have oil pressure is good then its a fair chance you have a bad sending unit otherwise its a bad oil pump. Replacing an oil pump is not hard if you ca get the pan off without lifting the motor, Otherwise this is a big job

This is pretty common on the older vehicles. There are three primary things it can be.

1. The wear in the bearings is enough to bleed pressure to the point at low pressure it just won't stay up high enough.
2. You have a bad sensor
3. Your oil pump is not pumping enough pressure.

Most of the time you don't have to worry about it. I would go to a heavy weight oil like 10W40, and I would switch to full synthetic. It works great on older motors.

Hope this helps.

Could be that your Oil pump is getting clogged or may not be fuctioning properly. Isnt getting enough power while at a low idle because its clogged.... When your stopped or in your driveway with the light on put your car in neutral and set the parking break and rev the motor up to 2200 RPM's and see if the light turns off.. If i does then that is most likely your problem.