Oil changes are an integral part of car maintenance. Synthetic oil, for example, is recommended to be changed every 6 months or 6,000 miles.
You might think it might be wise to save time or money by stocking up on engine oil or using some of your unopened motor oil. But you’re not sure about the shelf life of engine oil and now you’re probably wondering: “How long does engine oil last and Does synthetic oil expire?”
The answer is that synthetic engine oil goes bad over time. Synthetic oil shelf life is about 7 to 8 years, however, there are many factors that can increase or decrease the shelf life of oil, such as surrounding temperature and the storing temperature.
Table of Contents
Synthetic Oil Lifespan: How Long Synthetic Oil is Good for?
1. Synthetic vs conventional oil
The lifespan of your engine is dependent on the type of oil you choose. Synthetic oils are not only much better in terms of performance but also longevity compared to conventional oils.
Synthetic oils are much more refined and have more consistent molecules allowing them to last longer and degrade at a much slower rate.
2. How long does oil last in storage?
The shelf life of your oil in storage is dependent on the manufacturer and the storage temperature. Unused oil goes bad, however, the rate at which motor oil expires in unopened containers is much slower compared to when it is left sitting open.
On average, Synthetic oil loses its potency after 7-8 years. However, some manufacturers have different recommended shelf lives.
| Manufacturer | Shelf Life |
| Mobil 1 | 5 years |
| Amsoil | 5 years |
| Valvoline | No Expiry Date |
| Pennzoil | 4 years |
It’s important to note that Synthetic oil storage is best in cool, dry, and dark places at around 7-26℃.
3. How long does motor oil last once opened?
When you leave synthetic oil untouched after opening it, it can degrade over time. It is much more susceptible to the elements, humidity, and moisture. Opened motor oils can also be contaminated by dust and other particles.
Thefore, opened oil will only last for 2 years up to 5 years, depending on the oil quality.
4. How long does oil last in a car not driven?
Some claim that it can last up to 3 months, but you should not wait that long, that is to avoid the oil going bad.
In fact, oil in a stored car left for more than a month can oxidize and can form sediments.
The oxidation process can form acids that can corrode parts of your engine. When you take out your car from storage, it is important to do an oil change immediately.
5. Recommended time uses
Manufacturers might state that their synthetic oils last for a long period, however, the recommended use for car owners should be 7,500 miles up to 15,000 miles.
Factors That Affect the Lifespan of Synthetic Oil
Now that we know the answer to the question: does motor oil get old, here are some of the factors that affect motor oil expiration dates.
- Additives
The different additives that are infused can alter synthetic oil expiration and shelf life. Additives are mostly used to maintain viscosity and increase the temperature ranges of the engine oil. Here are some additives and their effects on engine oils.
| Additive | Effect |
| Copper and Iron | Catalysts that speed up oxidation
Lowers shelf life |
| Zinc | Allows the oil to endure higher temperatures |
| Pour Point Depressants (PPD) | Stops wax crystal formation at low temperatures |
| Detergents and Dispersants | Suspends contaminants and prevent sludge from forming |
| Alkaline | Neutralize acidic contaminants |
| Oxidation Inhibitors | Keeps the motor oil stable |
| Corrosion Inhibitors | Stops corrosion and prevent condensation |
| Calcium | Provides oxygen to the oil and delay sludge formation |
- Oxidation
Oxidation is the combination of oil and oxygen and is a major factor that can limit the synthetic engine oil expiry date. Oxidized oil can become very viscous and harder to pump. It can also reduce the transfer of heat and can block passageways inside the engine.
- Thermal Degradation
Thermal degradation happens when the oil cracks at high temperatures when it lacks oxygen. This can create deposits in metal surfaces and stops the oil from lubricating. Thermally degraded oil can also produce volatile gases and allows heat to build up.
- Contamination
Contamination, such as water and particulates, is another factor that affects the oil’s lifespan. Water-soluble materials and particulates can cause the oil to be rejected and can cause damage to the hydraulic system of your car.
Signs of Degraded Synthetic Oil
- The oil that goes bad might damage the car’s engine when kept there for a long time. You can face various issues, including:
- Acid formed in the engine
- Rust and corrosion
- Poor car performance
- Bad fuel efficiency
Now that we know the answer to the question, does synthetic motor oil go bad and its consequences, let us look at some of the signs and symptoms of degraded synthetic motor oil.
1. Check the expiration date
Most motor oil manufacturers include an expiration date label on their motor oil products. Some manufacturers post theirs online as well. These are good indicators to know if the oil is still good or not.
It is important to remember that these labels are meant for unopened bottles that have been stored correctly. The shelf life of synthetic oil can be far less if opened and inadequately stored.
2. Color and appearance
A fresh engine oil will have an amber color. When you find your engine oil dark or black it is a sure sign that the oil has oxidized. Dust and foreign particles are a sign of contamination. Good oil should be flowy and stable.
3. Consistency
Another sign of degraded motor oil is its consistency. Bad oil has the consistency of slime or sludge. It should not be too thick and must be fluid.
Proper Storage and Maintenance of Synthetic Oil
Synthetic oil might last long but without proper storage and maintenance, it can easily degrade. Here are some tips on how to properly care for your synthetic engine oil.
- Make sure that your engine oil bottle is in a cool dark place away from direct sunlight.
- Keep the oil in a place where the temperature does not constantly fluctuate.
- Keep the original bottle. Do not try to mix bottles with different engine oils.
- Remember to check the oil’s expiration date in the bottle.
- Do not mix engine oil with paints, solvents, anti-freeze, and other chemicals.
Frequently Asked Questions
How can I dispose of expired synthetic oil safely?
If you’re thinking of disposing of that 15w40 synthetic oil in the drain, then think twice. Some cities carry a hefty fine for wrongful disposal. You can instead drop off your oil to a local waste collector or to a car workshop.
Can I use synthetic oil past its expiration date?
Expired oil is not as effective and can cause serious damage to your vehicle. It can be extremely corrosive and can affect your fuel performance. Oil is recommended to be disposed of when it expires.
Conclusion
So does motor oil expire?
Synthetic oil can last for 8-10 years, however, some manufacturers suggest that synthetic oil should be used for around 5 years. Compared to conventional oils, synthetic can last for a very long time.
It’s important to remember the answer to the question “Does synthetic oil expire?” the next time you buy oil for your car.
Working with Vernon and Ryley has been a great experience for me. Together with the rest of the team, I hope to create reliable and useful information for our readers, no matter where they are and their experience with car maintenance.
