Will High Mileage Oil Cause Leaks [Discover Hidden Truth]

High mileage oil is the best friend of your old car with 75k miles. The old car engine requires a special oil that reduces engine pressure by preventing wear & tear, sludge, and deposits. And high mileage oils contain the additives your old engine needs. 

But, many vehicle owners ask this question- Will high mileage oil cause leaks as this oil includes detergents? 

Well, it’s a myth. Instead, quality high mileage oils prevent the oil leak by rejuvenating the degraded seal and reducing oil burn-off. To learn more about it, stick with this guide till the end. 

Will High Mileage Oil Cause Leaks

No, no oil (either it may be synthetic or high mileage) causes a leak. High mileage oil simply contains special additives like detergents and seal conditioners to support your old car engine. 

Now, you may ask- what causes the oil leak then? Well, high mileage cars tend to leak and burn off more oil compared to a new vehicle because of degraded engine seals. And your old car will get the benefit when you pour high mileage oil into your vehicle. 

The special additives of the high mileage oil help to rejuvenate degraded seals, reducing oil consumption and burning off. Therefore, old car engines tend to collect sludge left by other motor oils. To protect your car engine against sludge, high mileage oils will lubricate every moving part by breaking down & dissolving the sludge. 

Turns out, high mileage oils will protect your old car engine against wear & tear by keeping every engine component well-lubed. 

In short, high mileage oils never cause a leak. Instead, they will protect your old car engine by preventing oil leaks. In other words, high mileage oil is the recommended oil for high mileage cars

How Long Does High Mileage Synthetic Oil Last

Here how long the high mileage synthetic oil will last means how many miles you can go between each oil change interval. Generally, a well-performing synthetic oil will give you 10-15k miles between oil changes. 

But, it’s a bit confusing how often you should change the engine oil. It depends on your driving behavior. If you perform frequent or short trips more, you should change the oil often. On the other hand, you don’t need to replace the engine oil frequently if you go long-distance. 

However, you can get an extended oil change interval if you take care of your car according to the manual schedule. Due to engine break-in, the sharp edges and rough surfaces get soft, which reduces the chance of metal frictions. 

If you think pouring high mileage oil into your car can prolong the oil change interval, take the following advice into account. 

  • You should avoid changing the engine oil for an extended time if your engine burns oil. 
  • Never extend the oil change interval if you find the engine starts losing its pressure after conducting a compression test.
  • Don’t prolong the oil change interval if you don’t use a quality filter.

Is Synthetic Oil Better For High Mileage Cars

The short answer is- synthetic oil is not good for high mileage cars. Let’s describe why. 

Unlike newer models, the high mileage or old cars don’t have tight seals, gaskets, and other components. In other words, the older cars fail to handle the additives contained in high mileage oils.

Synthetic oil is efficient at cleaning the sludge. So, there is a possibility the synthetic oil may clear the deposits of your older engines that work as a seal. Consequently, it may cause an oil leak, and your engine burns more oil.

So, you need to check the oil level frequently and replace the oil often. Otherwise, it will damage your engine and other internal components. 

However, it doesn’t mean you should avoid pouring synthetic oil into your high mileage car. If you maintain your car properly, you can use synthetic oil in your old car. But we recommend you stick with the high mileage oils for your old cars. 

When To Use High Mileage Oil

Cars with 75000 miles get the most benefits from the high mileage oils. That’s why you should switch to high mileage oils when your car reaches the 75k miles mark. The additives high mileage oil include improving the overall engine performance by reducing oil consumption, protecting your engine against sludge & wear. 

However, we don’t recommend you go with high mileage oils at a specific mileage. If your older engine has no issues with regular motor oil, stick with it. You don’t need to spend extra bucks by switching to the high mileage oil. 

But, you must choose the high mileage oil if you get slow throttle response and less gas mileage. 


Now, you know it’s a myth that high mileage oil causes oil leaks. The truth is- high mileage oils stop oil leaks by strengthening degraded seals. Plus, they improve overall engine performance by keeping every engine component well-lubricated. 

However, we recommend you go to a certified car mechanic before switching to the high mileage oil for your old car engine. They will give you the best suggestion on what you should do and don’t. 

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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