Why It’s Never A Good To Just Top Your “Old” Engine Oil?

Have you noticed the engine oil light illuminating the dashboard when you drive?

If you have, this signals that your car has low oil pressure. And while there are several things that can cause a drop in oil pressure, the greatest culprit is low engine oil. 

Question is, can you just add oil to your car? Unfortunately, you can’t. You should only add oil if you’ve verified that your car needs an oil top-off and not an oil change.

More on this below:

Can you just add oil to your car?

No, you can’t. Adding oil without proper inspection can negatively impact its performance. 

To be more specific, the new oil can easily get contaminated by the old batch.

In fact, any impurities that were present in the old oil will continue to accumulate, making the new oil dirty within minutes.

Instead, you should first confirm whether your car needs a top-off or a complete oil change.

A top-off means you’re adding more oil to reach the recommended level.

Contrary, an oil change entails draining all the current oil and replacing it with new oil. Your mechanic will also install a new oil filter during an oil change

Replacing with new oil guarantees that the engine’s parts will be lubricated efficiently; hence, allowing your car to perform optimally.

So how do you know whether your car needs a top-off or an oil change? The easiest way to know is to check your oil on a regular basis. 

If you notice that the oil level is low, you can top it off.

But if you notice other engine issues like the smell of burnt oil, dirty oil, or a knocking sound from the engine, then your car needs an oil change. 

Why can’t you just top off your engine oil?

Still, aren’t sure why you should get the engine oil in your car replaced instead of adding more? 

Here’s the thing, oil breaks down gradually with use and this causes it to lose its efficiency. 

As it cycles through the engine lubricating the moving parts to prevent friction, this oil begins to disintegrate and wear out. So even if you add more, it won’t be as effective at reducing friction as fresh oil would. 

Another reason why you shouldn’t mix new and old oil is because of the risk of contamination. Over time, pollutants like dirt, and debris build up in the oil forming a sludge-like substance. 

The sludge can adhere to different parts of the engine; hence, compromising their function. To avoid this, it’s important that you get the oil changed and not just topped off. 

Does this mean I can’t add engine oil between oil changes?

Sure, you can. If you check the oil level using a dipstick and realize that it’s below the minimum mark, then you’re free to add some more. 

Under ideal conditions though, the oil level shouldn’t decrease by much between oil changes. If you find yourself topping it off more frequently than usual, there are likely more serious issues, such as:

  • You’re not complying with the manufacturer’s recommended maintenance schedule for changing engine oil
  • The car’s engine is burning high amounts of oil, which stems from other problems, such as faulty piston rings
  • Your car is experiencing an oil leak

What happens if you go too long without oil change?

The owner’s manual usually states how frequently you should get the motor oil changed. Initially, the rule of thumb was to do regular oil changes every 3,000 miles or so. 

But thanks to modern automotive technology, you can now drive up to a range of 7,000 to 10,000 miles before getting the oil replaced. If you exceed the recommended oil change, a number of things could happen, such as

  • Damages engine components – overly used oil contains an array of contaminants which makes it less effective at reducing friction. Due to this, the engine elements may start grinding against each other and this can lead to irreparable damage.
  • Nullifies your car’s warranty – if you recently purchased a new car, you should get the oil replaced as frequently as the manufacturer recommended. Failing to do this can cause your car’s warranty to be completely nullified. This then leaves you stranded without any assistance. 
  • Negatively affects the engine’s performance – during an oil change, it’s not only the oil that gets a replacement. 

Your mechanic also swaps the oil filter responsible for trapping dirt and debris.

So when you drive for too long without an oil replacement, these additives accumulate causing the engine to run inefficiently. 

  • This leads to fuel inefficiency – regular oil changes not only keep the engine in pristine condition. They also ensure that your car uses gasoline efficiently. If the oil is dirty or contaminated, the engine will be forced to work harder; consuming more gasoline in the process. So if you want to save money, stick to the stipulated frequency for changing the oil. 

So is replacing oil, instead of just adding it worth it?

Yes, it definitely is. By replacing oil, you’re ensuring that the engine will keep working optimally and consume fuel efficiently.

This prevents complete engine failure that would be more expensive to fix than simply getting an oil replacement. 

Best tips for adding oil to your car 

Once you’ve verified that your car doesn’t have enough oil, how do you go about adding more? Here are a few tips to guide you:

  • Park your car – the first thing you should do is park your car on flat, level ground then gather everything you need. These include the correct engine oil, a funnel, a towel, and a pair of rubber gloves. Next, allow the engine ample time to cool before opening the hood. 
  • Check the oil – locate the car’s dipstick. Oftentimes, the dipstick comprises a T- or loop-shaped handle and is found in the engine bay. It should be easy to find as it’s labeled “engine oil” in yellow. 

For the first time, you should pull out and clean the dipstick with the towel. Next, put it back until it clicks into position, and then pull it out again.

You can now check the oil level on the dipstick.

  • Take a reading – if the oil level is at or right below the “add” or “low” mark, it means your car doesn’t have enough oil, in which case you should add more. This is also the case if there’s no oil at all on the dipstick. However, if it’s past the “add” oil line or in the “full” region, you don’t need to top it off. 
  • Add oil – if you do have to add more, first locate the oil filler cap. This is usually a circular black cap labeled “engine oil.” Once you find it, remove it and place a funnel inside. Now all that’s left to do is to top off with the right oil. Just how much oil you’ll add depends on the current level. 

Experts recommend adding the oil in small increments to avoid overfilling.

Once you add the first amount, wait a few minutes so that the oil has time to reach the bottom of the engine. You can then recheck the level using the dipstick.  

If it’s still low, continue adding till you reach the proper oil level, then put back the dipstick and oil filler cap.

If you notice that the oil reading isn’t changing despite adding more, it’s better to go for an auto repair and get a more thorough inspection. 


As tempting as it can be, it’s not advisable to top off the engine oil without a proper inspection. You should park your car, allow the engine to cool, then use a dipstick to check the oil level. 

Only when it’s low can you top off this oil.

Otherwise, your car probably needs an oil change, especially if you’ve noticed a burning smell, a knocking sound from the engine, or very dirty oil.


Dean Alvarez, TireForge Head Author

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