How Accurate Are Car Oil Light Indicators?

Modern vehicles have so many warnings and lights that it can be hard to know what’s important and what’s not.

But when you start to see warnings about oil levels or oil issues, it can be hard to know if these should be acted on.

So how accurate are car oil light indicators?

Oil level lights are very accurate and you should check your oil immediately. Oil life reminders are just suggestions and are likely to be slightly overemphasizing the need for an oil change. 

I’ll take you through what the difference is between oil levels and oil life numbers, as well as what you should do when you get oil-related warnings from your vehicle.

How Accurate Are Car Oil Indicators? 

An oil light will come on when your oil pressure drops, which means if your oil light is on you should definitely be getting it sorted out immediately. Checking oil pressure is relatively low technology but very reliable for measuring oil levels.

  • If you’re running low on oil because of an oil leak this will trigger the oil level light to come on.

This is a warning that action must be taken as without having proper oil, a vehicle is very likely to run into serious issues.

Running on low oil is so catastrophic for an engine that oil light indicators tend to show the oil as being lower than it is. This is built into the system to encourage people to change their oil before it’s too late as well as trying to prevent damage from bad oil.

The system depends on oil pressure as the oil pump cannot function without it. As the amount of oil directly relates to the amount of oil pressure, it is a dependable way to accurately determine oil in the engine.

Checking the oil can be done by popping the hood and looking at the dipstick. It’s best if the car has not been running so that the engine is fully cooled and all the oil has drained back into the oil pan.

Put the vehicle on level ground, and locate the dipstick.

Pull the dipstick out and wipe it clean with a rag. Reinsert the dipstick fully, remove it again and then eyeball the stick to see the level of oil. You should have indicators on the dipstick which shows optimal oil levels, so make sure your oil is sitting between these.

If the oil level looks fine but you’re still getting an oil light going off, it may be time to get a mechanic to look at it.

Here’s a YouTube video showing you how to check your car’s engine oil.

Does Oil Life Indicator Mean Low Oil?

Measuring the remaining oil life or oil health is separate from measuring oil levels. Most vehicles already have a notification system for oil levels, measuring oil health is a relatively new feature.

Oil life indicators are different from oil level indicators. The former is available on select cars, whereas the latter is present in every car.

Oil life indicators are using different data sets and may not even directly measure or sample the oil. Instead, algorithms are used based on driving speed, engine use, and other factors depending on the manufacturer of the vehicle.

More advanced systems will factor in engine load, the number of cold start cycles, engine RPMs, conductivity of the oil, and a variety of information from other sensors.

These systems will even display a negative number or percentage next to the oil life to further encourage an oil change.

To have an onboard sampling system that actually looks at oil quality to determine its remaining lifespan would likely add $20,000 to the price of the vehicle.

Real-world testing has shown that there is a slight buffer built into oil life systems. A 2007 Honda Fit Sport was tested by Edmunds, a car review website. While it used to be called a maintenance minder, it seems now to be called oil life on Hondas now.

The vehicle’s oil life system came on at different intervals, at which point a different driving style was adopted. This reflects that the system is not just using miles driven as a benchmark, but considering the driving conditions, as well as other data.

After having the oil changed and analyzed, Edmund’s article states that analysis showed the oil had at least 2,000 miles of life left in it.

Can I Drive My Car With 0% Oil Life Showing On Dashboard?

Testing has revealed that the oil life indicators are made to be biased towards recommending oil changes.

Given the damage that can occur with bad oil, manufacturers have found that having systems which give the driver a warning to change the oil improve the lifespan of the vehicle. 

But to actually test whether the oil has remaining life is inconvenient and expensive, especially if you’re doing it every time the indicator goes off.

  • The system also must be reset when you change the oil, as the oil life indicator only uses secondary data such as engine revolutions to determine oil life. The process for this can be found in the manual, and a mechanic will do this when they service the car.

Once the indicator starts getting below 25%, it’s probably time to change the oil if you haven’t already done so per usual maintenance. At 25%, the system is estimating that your oil only has a quarter of its effective life left.

Ford recommends to change oil once the Oil Life Monitor lets you know it’s time for an oil change. This feature was only rolled out for 2008 or later models.

Check out our article that shows how to change your oil without needing to jack your car up. You can read it here.

What Is The Meaning of Oil Life %?

The percentage measures the estimated remaining useful life of the oil. With a fresh oil change, your system should be showing 100% oil life.

So at 80%, your oil still has 80% of its expected lifespan. The rate of change will be different according to road conditions, particularly mountain driving, lots of stop-start driving, and short distances.

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