Why Is Oil Coming Out Of Exhaust?

Smoke coming out of the exhaust pipes is not something that goes unnoticeable. Neither you nor anyone else on the road will miss that. But having oil come out of the exhaust is a whole different story. Oil coming out of car’s exhaust often indicates serious internal damage or worn down engine components. This article discusses the several causes of why the issue, oil coming out of exhaust happens so read on.

Why Is Oil Coming Out Of Exhaust?

Oil coming out of exhaust may be a warning sign that indicates that there is something wrong with your car. If you notice such a sign, make a professional mechanic check your car as soon as possible. This issue is quite common and is seen in a lot of used cars.  If the issue is simple enough, you can fix it on your own. Here are some causes that can create the issue of oil coming out of exhaust pipe to help diagnose the problem easily. 

1. Obstructed PVC Valve

The internal gases pass through the PVC valve to get to the combustion chambers. The compressed gases creates pressure due to the obstruction in the engine. This forces the oil to flow through several seals and into the exhaust pipes. Some other symptoms that indicate oil coming out of exhaust are bluish smoke and oil-smeared spark plugs. To fix the issue, you might have to replace the valve. 

2. Worn Valve Guides

Valve guides are responsible for managing the gas flow into and out of the engine. These valves are surrounded by seals around their shafts which wear with time. When this happens, the engine oil leaks through the exhaust pipe. A common symptom that indicates this issue is blue smoke coming out of the tailpipe. 

3. Ruptured Or Torn Gaskets

Head gaskets usually act as a seal between the engine heads and the blocks as it is a part of the exhaust system. A blown gasket however leads to one or more fluids coming out of the seal and mix into the exhaust stream. This can thus lead to oil leaking out of the exhaust pipe. 

The common symptoms of ruptured or torn gaskets that lead to oil flowing out of the exhaust pipe are reduced engine performance, excessive fuel burning and overheated engine. Replacing the defective gaskets is the only way to fix the issue. 

4. Soot Coming Out Of The Exhaust Pipe

Sometimes soot comes out of unclean exhaust pipe. A thick layer of soot is mixed with condition coming out of the exhaust pipe which strongly resembles oil. Thus vehicle owners often mistake this mixture for soot. The issue of soot coming out of the exhaust pipe happens when your car and the exhaust pipe are not given regular maintenance and washing. This issue is easily fixable. All you have to do is wear a glove and run a finger on the inside of the pipe to check if there is soot.

5. Worn Out Piston rings

Pistons are the parts in a car’s engine that is responsible for harnessing the energy from fuel combustion. Ignition of the fuel mixture forces them up and down in their bores which provides energy to move the vehicle. They are sealed in their respective bores by piston rings around their circumference which are lubricated by the engine oil. 

When these rings get worn, the seal becomes weak, making it easy for oil and fuel to leak past the rings into the exhaust system. The main symptom that indicates such an issue is the bluish or sometimes white smoke that comes from the tailpipe. There will also be a noticeable loss of engine power. 

6. Hole In Piston

As mentioned above, the piston is what is responsible for harnessing energy from combustion. But with time, like any other car components, the piston can also wear down. This can result in the generation of a hole in the surface of the piston. A hole in the piston will make it very easy for oils and fluids to escape into the exhaust system and make their way to the exhaust pipes. The problem will mostly be accompanied by blue-tinted or whitish smoke coming out of the tailpipes. Some other symptoms of the issue also include smoke coming out of the exhaust pipes, poor running of the vehicle, poor performance and engine noise.

7. Cracked Engine Block

An engine block is where all the internal parts of the engine are housed. It has all the passages that control the flow of fluids to its various working parts. A crack in the engine oil makes it easy for the oil and fuels in the engine to escape through them. This is quite a serious issue. The issue is usually accompanied by symptoms like overheating, loss of power, rough running and engine noise.

How To determine What Kind Of Oil Is Coming Out Of The Exhaust Pipe?

We have seen smoke coming out of our and others car exhausts. Sometimes the colour of smoke that comes out of the tailpipe varies. Observing these colour differences can help you diagnose the kind of problem your car is having. 

Black smoke is usually a product of unburnt fuel. This means that the internal combustion that is happening in the engine is incomplete which is not desirable. Blue tinted smoke or grey smoke indicates that there is oil leaking into the internal combustion engine. 

White smoke coming out through the exhaust pipe is one of the most serious kinds of problem and must require a thorough checkup. This issue has nothing to do with oil coming out of the tailpipe but it indicates some issue in the combustion chamber or faulty piston rings. 


For used vehicles, and the ones with a very long usage history, oil coming out of exhaust pipes is a fairly common problem. Frequent maintenance or inspection is important to ensure safe and hassle-free driving because more worn parts can be found as a vehicle’s mileage increases. This is one of the factors you have to put into consideration when deciding to purchase used vehicles. This article has discussed the most common reasons why oil can leak into a vehicle’s exhaust pipes. Hope you found it helpful. 

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