At What Oil Life Percentage Should Oil Be Changed?

by Synthetic Oil | Last Updated: February 22, 2023

In many modern vehicles, there is a way to look at the remaining oil life, such as Honda’s oil life percentage monitor. You may know that oil changes are essential, but at what oil life percentage should oil be changed? In most cases, 15-40% oil life is when your vehicle needs an oil change, but there are some factors that you need to consider.

Here is everything you need to know about oil life percentage, including when to change your oil and whether such indicators are reliable.

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When Should You Change Your Car’s Oil?

Back in the day (and still true for many car drivers), you needed to keep track of the mileage and look at the vehicle’s dipstick to ensure that the oil was not getting too sludgy. Usually, manufacturers and auto repair shops will recommend changing out your oil every 3,000-5,000 miles (or 3 to 6 months). However, some vehicles can go for 10,000 miles before an oil change without any damage done.

You just need to make sure that you do not go too far over an oil change because doing so runs the risk of engine damage.

As mentioned earlier, when the oil life indicator is between 15% and 40%, it means it is time for an oil change. The oil life indicator is like a countdown. It points to the moment when the quality of the oil begins negatively impacting the performance of your vehicle. Such indicators are taking into account your engine’s RPM, the number of cold starts, driving hours, and internal temperature to estimate how much oil life remains.

In Hondas and other makes, a maintenance reminder will start glowing on the dashboard once a certain number of miles or oil life percentage is hit.

How Long Does 15% Oil Last?

If your vehicle is around 15% oil life, you will get an estimated 750 and 1150 miles, averaging around 950 miles. However, this is based on a hypothetical range of 5,000-7,000 miles per oil change. Not every vehicle is going to fall into that range. Higher mileage vehicles may only get 5,000 miles, while vehicles using conventional oil may get around 3,000 miles before requiring an oil change.

If at any time your driving habits change, it could alter how much oil your vehicle consumes, thus draining the oil life percentage even faster than usual. For example, if you suddenly decide to go on a week-long road trip, that 15% oil life is going to drop rapidly.

Are Oil Life Indicators Reliable?

Oil life indicators are part of a monitoring system that is supposed to provide you, the owner, with insight into the health of your vehicle. The figure these monitors give you is not 100% accurate. Consider it more of an estimate.

Keep in mind that oil life monitors (OLMs), do not track oil level, oil condition, or oil quality.

However, oil life indicators are getting better and better when it comes to differentiating between normal driving habits and ones considered an emergency.

Oil life indicators also keep in mind severe driving conditions that would make the engine work harder. As such, you should trust that the percentage shown is a reliable reading. You can count on the percentage being within the right ballpark. So if it is below 15%, don’t assume that is correct.

Check out this opinion on oil life indicators from a mechanic:

How Driving Conditions Affect Oil Life Percentage

Continuing on with the discussion of whether oil life monitors are accurate, let’s consider what these systems track. Oil life monitors log conditions like driving habits and climate. The computer also contains an algorithm that calculates trip time, engine temperature, engine load, idle time, mileage, and much more. Using this data, the algorithm then establishes an oil change interval. If your car is brand new, that oil change interval is going to be low, around 3,000 miles. As the algorithm logs for information, that oil change range may go up to 10,000 miles (never higher).

However, most OLMs will establish an oil life range of 5,000 to 7,000 miles.

That is because your driving habits change throughout the year. Consider how your routine changes in the winter and summer. You go from warming up your car before work to just hopping in and driving off. During the winter, the algorithm calculates a decreased oil change interval, because your idle time has increased dramatically. Plus, cold weather and frequent short trips, such as a short drive to the grocery store, impact your engine more than longer operating times and less idling.

Is It Bad To Drive With Low Oil Life?

Yes, it is bad to drive around when the oil life of your vehicle is 15% or lower. The main purpose of oil is to lubricate the engine. When you don’t have enough, the oil may be spread too thin. It may also be too sludgy to work effectively, causing the engine to grind and build more heat from friction than usual. That can cause damages that greatly impact the performance of the vehicle. It can also cause other issues that cost a fortune to repair.

What Happens If The Oil Percentage Hits 0%?

At what oil life percentage should your oil be changed? Not at zero. Once the oil life percentage hits 0%, it is only a matter of time before your engine gets damaged.

Final Thoughts on Oil Life Percentage

Usually, between 15% and 40% oil life percentage is when your oil should be changed. You do not want your car to get much lower than 15%, because your engine oil deteriorates much more quickly. Stay on top of your oil changes. You should be able to keep your engine operating wonderfully for years to come.