Does Motor Oil Expire? Know When to Change your Oil

Motor oil. The lifeblood of any vehicle. It keeps all the moving parts of your engine lubricated, cooled, and running smoothly. But, like all other fluids, motor oil will eventually break down and need to be replaced.

The question is: how long does motor oil last? Unlike other fluids in your car which have an long lifespan like coolant and brake fluid, motor oil does have an expiration date not too far down the road. Motor oil will eventually break down and lose its effectiveness, even if it's never been used. And when it's time to change it, be prepared to pay $35-$75 for conventional oil and almost double at $65-$125 for synthetic oil.

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Signs It’s Time to Change Your Motor Oil 

  • The oil change reminder is lit 
  • Your car is making a knocking noise 
  • The oil light comes on 
  • Your car is using more oil than usual 
  • The Check Engine light is on 
  • Your car’s engine feels sluggish

How Long Does Motor Oil Last? 

Nothing last forever and motor oil does have an expiry date. However, this date is not an absolute indicator of when you need to replace your oil. The expiry date is simply the point at which the motor oil starts to degrade and lose its effectiveness. 

How long does motor oil last then? On average, conventional motor oil lasts about five years on the shelf in unopened containers. Semi-synthetic and synthetic motor oils will last seven to eight years. However, these are just averages. The actual lifespan of your motor oil will depend on several factors, including how it is stored and the type of oil it is. 

Synthetic vs Conventional Oil: Which One Lasts Longer? 

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Synthetic vs Conventional Oil

When talking about motor oils, there is no doubt that synthetic oil is superior to conventional oil. Synthetic oil is made from highly refined base oil mixed with a blend of different chemicals and detergents, which makes it more resistant to breakdown and degradation. 

Conventional motor oil, on the other hand, is made from crude oil that has been refined to a lesser degree. The molecules aren’t as consistent a size as synthetic oil. This means that it is more vulnerable to degradation and will break down faster than synthetic motor oil. 

If you’re looking for an oil that will last longer and perform better, synthetic oil is the way to go. However, it is important to note that synthetic oil is more expensive than conventional oil. 

How to Tell if Your Engine Oil is Bad? 

There are several telltale indications that your engine oil may be bad. This subject can be broken up into two sections: used and unused motor oil. 

Used Engine Oil 

Used engine oil refers to motor oil that has been used in an engine. The biggest indicator that your used motor oil is bad is the color. Fresh, new oil is usually a light amber color. As it breaks down, it will start to turn dark brown or black. 

Another indication that your used motor oil is bad is the texture. If your oil feels gritty or thick, it has most likely started to break down. Of course, one of the biggest indicators used to tell if engine oil is bad comes down to the number of miles it has been used. 

Unused Engine Oil 

Unused engine oil refers to motor oil that has not been used in an engine. The biggest indicator that your unused motor oil is bad is the expiry date. Unused motor oil will start to degrade and lose its effectiveness after a certain amount of time. 

Most engine oils will have an expiry date printed on the bottle. However, if there is no expiry date, you can generally the production date on the jug and tack on an additional five years to that. 

So, does motor oil expire? The answer is a definite yes. However, the expiry date is not an absolute indicator of when you need to replace your oil. The expiry date is simply the point at which the motor oil loses its lubrication properties. When in doubt, swap it out. 

When Should You Change Your Oil? 

When should you change your oil?

In general, most motor oils will last for about 5,000 miles before they need to be replaced. However, if you drive frequently or in harsh conditions like in hot weather or on dusty roads, then you may need to replace your oil more often. AutoZone recommends periodically checking the oil level and quality in other to get the most accurate estimate for how often to change your oil. 

To check your oil level, simply remove the dipstick from the engine and wipe it clean with a rag and re-insert all the way in before pulling it out again. The oil level should be somewhere between the “full” and “add” marks on the dipstick. 

On newer models, the oil level can be checked via the infotainment system, eliminating the need to get your hands dirty. If you’re unsure about when to change your oil, it’s always best to consult your owner’s manual or a professional mechanic. 

Final Words 

At the end of the day, does motor oil go bad? The answer is yes. No matter if it’s tucked away in your garage or being put to work protecting vital components in your car’s engine, always make sure it is used within the “best before” date. 

Get the right motor oil for your car with AutoZone and ensure that your engine is properly protected. We have all the necessary tools and advice you need to do the job right. 

Frequently Asked Questions 

Does Motor Oil Degrade If Not Used?

Yes, motor oil does degrade if it is not used. Unused motor oil will start to break down and lose its effectiveness after a certain amount of time.

How Long Can Motor Oil Sit?

Once opened, motor oil will be good for 2-5 years. if unused during that timeframe, it will start to break down and lose its effectiveness.

How Long Can You Go Without an Oil Change?

Most motor oils will last for about 5,000 miles before they need to be replaced. However, it may need to be done sooner if driving in extreme conditions. Base your oil change intervals on the recommendations from your vehicle’s maintenance guide.

Does Synthetic Motor Oil Expire?

Similar to conventional motor oil, synthetic motor oil does expire. Luckily, it has a longer lifespan than conventional oil and can last seven to eight years.

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