Does engine oil go off?
Tom Vondrasek | 25th May 2023 | 5 minutes to read
Surprisingly, engine oil does go off. Whether it is sitting in a bottle in store or in the sump of your engine, it will not last forever. If you think about it, the oil is refined or blended and mixed with additives so these can impact how long it lasts. Then there are other factors, is the oil bottle sealed or open? How and where was it stored? How does that compare to once it is in an engine and being used?
We know oil deteriorates with use, though if you have a classic car stored for months and start it only 3 times a year, how long will the oil last?
Engine oil bottles are stamped with batch numbers and manufacture dates. These are there to help oil suppliers trace issues or problems if a batch has a fault in manufacture or packaging. It is not a use by date like you find on food in a supermarket — it does help you work out how old the oil is. Some only have the batch number so the manufacture date is not on the bottle. They are not always easy to decipher, and you may need the oil company’s help.
There are a lot of factors to consider when dealing with old engine oil and we’ve got answers to some common questions below:
Does Engine Oil Have a Shelf Life?
Engine oil does have a shelf life, so even if it is unopened, it will only last for so long. Most engine oils have a recommended shelf life of 5 years, though it can be longer depending how it is stored. For instance, Castrol’s engine oils last for 5-6 years, but this timeframe is specifically for oil stored in the original packaging in an ambient temperature environment.
Storage is important. Oil should be stored in an area where the temperature is consistent and does not go from boiling hot to freezing cold and not exposed to direct sunlight or moisture. Ideally a cool, dry, shaded environment out of the weather.
Something else to note is that synthetic oil will last longer than mineral (conventional) oil due to the different processes used to make it. The other side to this is synthetics are more expensive so, where you gain on one hand, you lose with the other. It does mean less downtime if the vehicle is used regularly.
The good part is that because you generally replace your engine oil regularly, this is not a common problem, though it is handy to know. This is especially true if your engine uses oil and you need to top it up on a regular basis — how long have you had the top up bottle?
How Long Does Engine Oil Last?
Oil will last for different amounts of time depending on how and where it is stored. Here’s a rough guideline for how long your oil will last in each circumstance.
Oil in an Unopened Bottle
Unopened and correctly stored oil can last longer than the 5 years. As engine oil is changed so often, it would be unlikely that the oil you have is over 5 years old, but in the event that you’ve had some sitting around for a while, this is your cut-off according to most manufacturers.
Oil in an Opened Bottle
Oil in an opened bottle will last approximately one year, as once you introduce air into the bottle, it contaminates the oil. Air can have moisture, dust, and impurities that can start to degrade the oil and cause it to be less effective, so it’s likely not worth the risk to put unopened oil that’s more than a year old into your engine.
Oil in an Engine
This one is pretty easy to figure out, as the vehicle manufacturer will specify service intervals based on mileage and time. Whichever one you reach first is when you should change the oil.
If you have a car that is in storage or used sparingly then it is worth consulting the experts on what you should do as far as oil changes go. The reason being that a turbocharged engine will differ from a normally aspirated engine and a high-performance competition engine will differ from a street engine.
What Happens if You Used Expired Engine Oil?
If you use old, unused oil in your engine it can increase wear and corrosion as the oil is past its prime and will not be as effective as it once was. The viscosity can change (usually it will get thicker), and additives can deteriorate and not work as well as they should.
If you suspect that your old oil might be no good, before adding it to your engine, pour some into an old glass. It should be a light transparent golden brown and flow readily. Whereas, if it is dark coloured or foggy and the flow is not smooth, do not use it. Even the smell may have changed and can be a way to tell if your oil has gone south.
If the oil is at all suspect, it is best to err on the side of caution and put in fresh engine oil. Your engine is too expensive an investment not to do it.
How to Dispose of Used Engine Oil?
Unfortunately, we don’t offer oil recycling at Repco stores for the moment.
Waste or old engine oil should not simply be poured down the drain. The best thing to do is put oil from the drain pan back into an old oil bottle and use the lid to reseal it. If you go to your local council website, they will have places to go where you can drop old oil off to be recycled.
Please use an old oil container and not a milk carton or soft drink bottle.
For more information on how to dispose of old oil, check out our article on proper disposal of engine oil, and if you need engine oil, head into a Repco store or shop online to see our full range.
