Updated at: 21-03-2022 - By: Lucas

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What happens to synthetic oil over time? According to numerous studies, nearly everything we use or consume has a best-before or expiration date. Thus, this suggests that everything has a shelf life after which it begins to break down or decay (whichever word you wish to use).

Additives and other compounds are commonly used in the production of motor oils in order to aid in the achievement of the oil’s intended function. Disintegration is a possibility for these additives and compounds (after a while).

As a result, pressure and other factors will cause synthetic oils to degrade over time. Unused oils, on the other hand, have a longer shelf life and are therefore safer for your engine.

Does Synthetic Oil Degrade Over Time?

The short answer is YES, and we’ll go through why today. Compared to normal motor lubricants, synthetic oils have fewer contaminants. As a result of this, synthetic oil can be used for up to 15,000 miles before it needs to be changed out.

When using standard oil, you’ll need to replace your oil every 7,500 miles or so, which is a lot of oil. Regular oils spoil/degrade more quickly than synthetics because of the higher level of contaminants.

In contrast to this, the explanation above relates to the introduction of oil into the vehicle. To put it another way, the conditions under which these oils are used are so intense that they degrade.

Do synthetic oils that haven’t been used degrade over time as well? There is no doubt about that; the answer is yes. Total claims that unused motor oil can degrade for up to two years after being stored. As a result, the chemicals and additives will inevitably break down during this time period.

However, Mobil claims that unused motor oils can last up to five years before they are no longer safe to drive. As can be shown by comparing the data from these leading motor oil manufacturers, motor engine oils (in general) will degrade after a period of time beyond three years (on average).

Would The Oil In My Parked Car Degrade Overtime?

Does Synthetic Oil Degrade Over Time-2

Others have many vehicles, many of which are parked in their garages. This is similar to unused oils in this scenario (explained above). It can take up to two years or more for a car’s oil to begin to degrade if it is not being driven.

It is important to change the oil after the manufacturer’s recommended mileage if you take your car out for occasional drives.

How Do You Know That Your Oil Has Gone Bad?

The expiration date on the motor oil you bought a while ago can tell you whether or not it’s still good. The expiration date should be clearly visible on the label or the bottom of the gallon, depending on how the product is packaged. If the oil has a poor colour, you can tell right away.

It’s also possible to check for spoiled motor oil by pouring it into another container and inspecting the bottom for any deposits.

When an oil’s additives degrade, they settle to the bottom of the container. In cases when the oil has been sitting for some time before being deemed suitable for use, this is a good idea.

What Will Happen If You Used An Expired Oil?

Expired oils should never be used in any automobile engine, regardless of the manufacturer (whether new or old). These compounds become highly poisonous or corrosive when the additives degrade or decompose.

Expired oils, on the other hand, may encourage oxidation and cause leaks, wear, and tear in your engine instead of protecting it.

If the oil has not been contaminated by water or any other liquid, some mechanics argue that expired motor oils offer no danger.


Over time, engine deposits contaminate synthetic oils. If you’re driving an older vehicle, you should replace the oil every 7,500 miles or so. These engines produce more contaminants and deposits than contemporary engines because of this.

Additionally, it’s a good idea to replace the oil filter on a regular basis. An engine failure can occur if you continue to use the same filter after multiple oil changes.

As a result, does synthetic oil wear out? Not at all (whether used or not used). The oil’s additives have a 5-year shelf life. Always look at the manufacture and expiration dates on motor oils before making a purchase.