Oil in Intake Manifold: What to Do and How Bad It Is? (Read!)

The intake manifold is an engine that supplies the fuel/air mixture to the cylinders. It’s a series of tubes ensuring that the air coming into the engine is evenly distributed to all the cylinders. Now, since it distributes air and fuel, you may find it problematic to see oil in your intake manifold. So, you may ask:

What should you do if you have oil in the intake manifold, and how bad is it? If you have oil in your intake manifold, it can be a sign of an underlying issue. For example, your oil may be leaking so bad that it reached your intake manifold. Whatever the reason is, you’ll need to check and fix it as soon as possible.

The presence of oil in an intake manifold means you have oil leakage in your system. For this reason, you’ll need to have it thoroughly checked so you can make sure that the oil will remain in areas where it’s supposed to be.

In this article, you’ll see an in-depth take on the intake manifold and the issues you may have if you have oil in this particular part. This way, you can understand what to do and the best response to fix it soon.

Without further ado, let’s get into it!

Oil in Intake Manifold

Can Oil Leak From Intake Manifold?

Yes, oil can leak from the intake manifold. It is because the engine oil has specific passages that help distribute it to parts that need lubrication. However, the intake manifold isn’t a part of it. 

If you have oil in your intake manifold, chances are you have an oil leak in your system that you need to fix soon.

In general, when the engine oil cannot flow freely through its supposed pipes, it gathers in the cylinder head’s top. The oil will flow through the PCV valve and into the air intake manifold after completely closed the channel. 

Another thing to note is that your intake manifold gasket can cause leaking of both coolants and engine oils. If such an issue occurs, you have to remove the intake manifold and replace it with the gasket.

Should I Have Oil In My Intake Manifold?

No, you shouldn’t have oil in your intake manifold. If you do, it’s a sign of an underlying issue, and it’s likely an oil leak.

In general, you shouldn’t worry if you only see a slight coating of oil. It happens inevitably, and you can’t help it. However, if you see a puddle or a small oil stock in the manifold, you may want to take it to a service center.

If you see a massive reserve of oil in your intake manifold, it can be a sign of your engine getting worn out and not functioning to the best that it can.

How Bad Is It to Have Oil in Intake Manifold? 

Having oil in the intake manifold can be a simple issue and a complicated one. In general, it depends on the amount of oil you have in it.

For instance, a slight coating of oil is alright, and it happens from time to time. However, it’s not a sign of any problem, and you can continue using your car without doing anything about it.

However, if you see your intake manifold with small puddles of oil, then that’s something you’ll need to check and fix soon.

This issue does not require immediate attention because it will not result in something deadly very soon. However, this indicates that your engine is beginning to show its age, and you will most likely need to replace numerous components.

In general, it is preferable to get it diagnosed in a mechanic’s shop. They can better advise on which parts need to be replaced or repaired.

What Causes Oil in the Intake Manifold?

If you have oil in your intake manifold, you may suspect either of these two problems as the cause:

Worn-out PCV Valve

If you have oil in the intake manifold, the PCV Valve is the first part to investigate. Still, a tiny quantity of oil in the air intake manifold should not cause concern.

Stuck PCV valves are relatively uncommon in automobiles with fewer than a hundred thousand kilometers. Therefore, you must investigate the entire PCV system. A defective one will create an airflow imbalance and oil to enter the air intake.

The check engine light will illuminate as well. If one or more valves are totally blocked or partially functioning, cleaning or replacement is a possibility.

Clogging in the oil passage

The next probable cause of oil reaching the intake manifold is the clogging in the oil pipes or passages.

If you don’t replace the oil in your automobile, it will gather muck and deposits in the oil channel and leave them there. If the oil cannot start flowing through the channel, it collects in the cylinder head’s surface.

The oil will flow through the PCV valve and into the air intake manifold after completely closed the channel. Add an engine flush solution into the oil and run the engine several times to solve the issue.

Clean the air filter and replace the engine oil once the accumulation has been removed. If this does not resolve the problem, seek the assistance of a mechanic.

How Do You Get Oil Out of Intake Manifold?

The best way to get the oil out of the intake manifold is to remove the intake and clean it using your degreaser choice. It may take a while, and it’s a lot to do, but it’s the best way to clean out the oil.

The other option is to clean the intake manifold using a decent carb and fuel injection cleaner. Next, remove the intake air tube connected to the intake/airbox from the intake/airbox. 

Lift the throttle plate and spray oil anywhere you can see it with light. Allow a few seconds for it to settle before reattaching the tube and starting the automobile. 

The process will produce a lot of smoke, and it’s completely normal, so you won’t have to worry. After a few moments, the smoke should eventually cease! 

How Do I Know if My Intake Manifold Is Leaking?

If you want to know if your intake manifold is leaking, you can check for signs or symptoms of such. Among the things you can look for are the following:

  • Backfires and harsh idling due to differences in the air-to-fuel ratio
  • Engine oil with a milky appearance
  • Coolant leaks onto the ground underneath while idling
  • Overheating of the engine regularly

If you think you have oil leaks in your intake manifold, have it checked by a mechanic soon so you can avoid further issues from arising.

How to Prevent Having Oil in Intake Manifold?

The best way to prevent oil out of your intake manifold is thorough and regular cleaning. These simple routines mentioned above go a long way in preventing engine oil from seeping into other parts of your vehicle, particularly the intake manifold.

Don’t waste your time and effort if you observe any of the probable reasons listed above or if you believe one or two of them are now affecting your car. 

Also, if you don’t have any mechanical experience, don’t attempt to fix the issues without any help. 

As always, don’t hesitate to get assistance from a mechanic near you. In this situation, that is the best course of action. 


In a nutshell, the oil in an intake manifold is a sign of oil leakage and a sign that your engine begins to wear out. The gravity of the issue depends on the amount of oil you have in the inlet manifold. 

If you have a slight oil coating, you can wipe it and do nothing more about it. However, if you see puddles of oil stuck in it, then you might want to take it to a mechanic for a thorough cleaning and to repair any leakage that’s happening.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more