Switched To Synthetic Oil Now Leaking [Know The Reasons]

Switched to synthetic oil, now leaking! It’s a general leaking issue every old car owner encounters. Generally, if you have a car with 73,500 miles or more, you will experience an oil leak. 

It will cause oil leaks because the regular oils fail to clean the engine gunks and deposits. When you put synthetic oil in the engine, it removes the deposit buildups and reveals the bad gaskets & seals. Consequently, the oil leaks through the damaged seals & gaskets. 

Here in this guide, we will elaborately discuss this issue and break down the following things: 

  • Is it normal for oil to leak from a car after an oil change?
  • Does Switching To Synthetic Oil Really Cause Leaks? 
  • And a lot?

So, keep reading between the lines. 

Switched To Synthetic Oil Now Leaking [Know The Reasons]

It’s pretty common to have an oil leak once you switch to synthetic oil. Though it’s a myth, it is a regular occurrence for older cars, especially ones that are upon the age. It happens because the seals and gaskets on an 80s car have often hardened up, and they get swelled or shrunk. 

When you add synthetic oil to a high-mileage car, the seals allow the oil to flow easily to leak past the seal. On top of this, the seal material gets degraded over time by wear & tear. As the synthetic oil cleans so well, it eats away the seal material fully. Consequently, the existing leaks become more noticeable, and oil starts dripping through the leaks. 

Our suggestion is to address the leaks caused by oil change to fix this issue. If your car is too old, it will be best to switch back to the oil you are using over the years. It will stop the oil leak.

Note: You can also read how to fix Kohler’s command engine oil leaking problems

Is It Normal For Oil To Leak From A Car After An Oil Change?

Yes, it’s normal if there are a few oil drips after an oil change. It happens from residual oil from parts below the drain plug that you don’t clean evenly. You don’t need to worry about this as it’s normal and causes no damage. 

Therefore, a small amount of oil may spill over during the filling process. And guess what, gravity brings the oil down to the bottom of your car. 

A loose filter, missing O-ring, or damaged O-ring are also responsible for oil leaks after an oil change. 

Fortunately, the oil leaks you will get after an oil change are easy to fix. So, address where the oil is leaking from and solve them.

Does Switching To Synthetic Oil Really Cause Leaks?

It’s a myth, which is far from reality. Generally, oil swap from regular or conventional oil to synthetic doesn’t cause any leak. Yes, it’s true synthetic oil is thinner than regular oil and it flows easily. As a result, it leaks past the spot more than conventional oil which is prone to leak. 

The cleaning ability of synthetic oil is superior to regular oil. It cleans the deposits and sludge from the engine that actually works as a seal in an old engine. When you put synthetic oil in the engine, it removes those deposits and makes the leak noticeable. Consequently, the oil starts dripping into those spots. 

Moreover, the seals and gaskets on the old car get damaged over time due to heat and wear & tear. When you put in new oil that contains new additives, it finishes those seals & gaskets completely. In return, oil starts leaking from the decayed seals & gaskets. 

However, synthetic oil causes no leak in a new car or the conditions of the seals and gaskets are in good condition. 


What happens when you switch from regular oil to synthetic?

Switching from regular oil to synthetic will maximize the engine protection as it flows easily to every moving part of your engine and lubricates them. On the other hand, it may cause a leak if you put the synthetic oil in a high-mileage or too old car. 

Can synthetic oil make seals leak?

Yes, synthetic oil could cause a leak if your car is too old. This oil can break down and eliminate deposits from the engine that will reveal the bad seals, which lead to leaks. 

Does synthetic oil stop leaks?

No oils (it may be synthetic or regular) can’t stop leaks. Good oil seals and gaskets can only stop the oil leaks. 

Does synthetic oil swell seals?

No, synthetic oil can’t swell seals. However, synthetic oil may cause a leak if your car is old by decaying the bad seals & gaskets. 

Can thin oil cause leaks?

Thin-oil can flow easily. If there is a bad gasket or seal, this thin oil can make its way into those seals and drip. However, if the gaskets and seals are in good condition, thin oil fails to leak through them.

Will an oil change stop an oil leak?

No, an oil change can’t stop an oil leak. What you need to do in this regard is- find out the leaking point and take the necessary repairing steps to stop the leak. 


Now, it’s clear why switching to synthetic oil causes an oil leak. If you add this oil to an old car, the oil will start coming down the bad gaskets as synthetic oil removes the engine gunk so well. 

However, synthetic oil causes no leaks if the seals and gaskets of your car are in good condition. If your car is too old, we recommend switching back to the regular oil. It will stop the oil leak.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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