Will Synthetic Oil Cause Engine Oil Leaks?

I worked at an oil change station. People asked this question every day about synthetic oil. So in this blog, I will try to answer one of the most asked oil-related questions.

Question # 1.

Will synthetic oil cause oil leaks on my engine?

This is not true now but for all of us old-school grumpy guys like me! This was a fact and a problem in the past.

Difference Between Conventional and Synthetic Oil

To better understand this let’s look at the difference between synthetic oil and conventional oil in a simple way. For this example, let’s pretend you were holding synthetic oil molecules in one hand and conventional oil molecules in the other.

Synthetic oil molecules would look like round ball bearings and conventional oil would look like oddly shaped gravel.

Now imagine those molecules flowing along inside your engine, which one do you think would flow better, faster, and with less effort? Obviously the ball bearings.

The Difference is the Reason

The molecules in synthetic oil are more uniform to those of conventional oil, Synthetic oil can move around your engine easier and thru smaller orifices.

This is very important for engines with turbo since synthetic oil can quickly reach these components to lubricate, reduce heat and protect. But in the past, when synthetic oil was first introduced, it was an issue because of these qualities.

Older engine gaskets were made of cork and cardboard, so with the properties of synthetic oil and its ability to flow easier thru smaller orifices oil leaks were a common problem.

It also led to the belief that synthetic oil is thinner than conventional oil (another question I get asked regularly).


With the introduction of modern engine gaskets made of silicone, synthetic rubber, and composite materials that are impervious to oil. this is no longer an issue.

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