Engine oil is the lifeblood of your car. Without sufficient oil or oil pressure, the engine can wear itself out in a matter of seconds. Besides lubrication, engine oil helps with cooling, sealing, cleaning, and protecting engine components from repeated impacts.
Every time you start your car you see a host of lights illuminate like a Christmas tree and then turn off almost immediately. The reason for this is to check if the lights themselves are working and to actually check the system they are attached to, if all is okay, then they turn off.
Some are informational while others are warning lights with the oil light being in the latter category. Car manufacturers use an oil pressure warning light on the dashboard to warn the driver if the oil pressure gets too low. Some cars are able to distinguish between low oil levels and insufficient oil pressure so you will know if the pump is malfunctioning or if you just need to add some more oil.
Unless otherwise noted, the oil light on the dashboard means your oil pressure is dangerously low. Of course, the pressure could be low because you do not have enough oil in there too. Where all the oil went is another day’s story and you need to top up to the required level.
Oil pressure can also be low because your oil pump is failing and your engine bearings are all worn out or they’re too loose to maintain pressure or for a number of other reasons none of which are good news.
So, when you see the oil light on when your engine is running or you are driving along, that means your pressure is low, and you will without delay want to pull over and shut off the engine as quickly as it is safe to do so.
Sometimes you will see the oil light flicker, especially when you are at idle like at the traffic lights. That is when oil pressure is at its lowest anyway. It is a sign that you are on the verge of having a serious problem.
There are a few cases where the oil light comes on simply because the oil pressure sensor is bad. That is a lucky break, although that sensor is very robust and rarely fails. By and large, seeing the oil light come on while you are driving is bad news. And it is a light you never want to ignore.
On the other hand, lots of newer cars also come with an oil level light, which is different. That is not an emergency warning light. It is more of a maintenance reminder light. The oil level light is designed to eliminate your need to check your oil with a dipstick.
Checking the oil used to be a regular task for car owners. But most people do not want to do anything other than starting the car and drive these days. Over the years, we have made clear to carmakers that rolling down our own windows or taking the key out of our pockets is way too much trouble, so many of them have eliminated the dipstick and replaced it with a sensor.
If your car has an oil level light, and it comes on, that is just a sign that you need more oil. It is usually not an emergency. That light will normally come on when you are down a quart.