Oil Coming Out Of Exhaust: Causes, Fixes and Prevention Tips

Table of Contents

1 Reasons Why Oil Is Coming Out Of Exhaust
2 How To Fix Oil Coming Out Of Exhaust
3 How to Prevent Oil to Come Out Of Exhaust?
4 FAQ Section

Discovering oil coming out of the exhaust shouldn’t be a cause for panic. This is a common problem for older cars. There are many methods to identify and resolve this issue of oil leakage in the exhaust, often manageable even from the convenience of your home without the need for a professional mechanic.

If you see oil coming out of your car’s exhaust, it’s not normal and can be a problem. Engine oil shouldn’t be coming out from the tailpipe. To keep your car in good shape, you need to figure out why this is happening and fix it. Finding the cause and taking early action is essential. This article explains the major causes of why oil comes out of the exhaust and how to fix it.

Reasons Why Oil Is Coming Out Of Exhaust

The engine oil may come out of the exhaust due to different reasons, such as a bad PCV valve, blown head gasket, damaged pistons, cracked cylinder head, leaked piston rings, or a faulty turbocharger.

Let’s explain the causes of engine oil coming out of the exhaust.

1) Bad Turbocharger

As the turbocharger of your car malfunctions, it may cause oil to leak into the exhaust. In most cases, this oil starts to burn in the combustion chamber, which results in predominantly blue or black smoke being expelled.

A defective turbo will also lead to reduced acceleration, poor fuel economy, poor engine performance, and the illumination of the check engine light. Moreover, a bad turbocharger may also produce distinct siren-like noise coming from the engine.

2) Damaged Pistons

The engine piston plays a crucial role in generating reciprocating motion to rotate the crankshaft, as well as compressing the fuel-air mixture prior to ignition. As the piston goes bad, oil can leak and make its way into the engine cylinder.

When the oil combusts in the combustion chamber with the fuel-air mixture, it starts to come out of exhaust in the form of blue smoke. This leads to potential engine damage and increased emissions.

3) Bad Valve Seals

Valve seals play a crucial role in maintaining oil within the crankcase and preventing it from entering the combustion chamber. When the valve seals become faulty, your car starts to emit blue smoke from the exhaust.

This issue may also lead to poor fuel economy and oil on the spark plugs. Additional symptoms include diminished acceleration and irregular idling.

4) Bad PCV Valve

The PCV valve of your vehicle has the job of discharging exhaust gas and any unburned fuel from the engine. When this valve is clogged, the gas volume escalates and creates an excessive amount of pressure.

In situations where oil seeps into the exhaust due to a faulty PCV valve, it generally creates blue smoke. Signs of this issue may also include spark plugs coated with oil.

Read More: Bad PCV Valve Symptoms and Causes

5) Blown Head Gasket

A blown head gasket is one of the major causes of the engine oil to come out of the exhaust.

The head gasket is installed between the cylinder heads and the engine block. It acts as a seal. If this seal is damaged, the oil may leak out and get into the exhaust system. When oil goes where it’s not supposed to, you might notice it coming out from the exhaust. If the leak keeps happening, the oil level in your vehicle might go down.

However, a bad head gasket can make your engine overheat. It can also make your car use more fuel than usual and perform worse.

6) Bad O Rings

Faulty O-Rings, often referred to as oil rings, may trigger issues of oil coming out of exhaust in your vehicle, leading to oil spillage while driving.

O-Rings are specific types of rings positioned on the engine’s pistons. The function of the O-Rings is to prevent oil from leaking into the engine cylinder from the oil pan. If oil seeps through these rings, it may produce different issues in your engine, leading to oil burning.

Oil burning is among the most common issues in IC engines. This is primarily because many oil rings of these engines lose their ability to retain the oil. Consequently, the oil slips past these rings and goes into the combustion process.

If your car’s oil is coming out of the exhaust, it indicates that your O-Rings are damaged or completely sealed off.

7) Cracked Cylinder Head Or Engine Block

A cracked cylinder head or engine block is also one of the major reasons for engine oil to come out of the exhaust. The cracked cylinder head or engine block provides a route for the oil to leak out, which then blends with exhaust gases and is released as blue smoke through the exhaust pipe.

If this issue is not addressed promptly, the crack in the engine block or cylinder head may lead to the failure of the engine.

8) Bad Valve Guides

Valve guides are responsible for regulating the flow of gases into and out of the engine. Over time, the seals around the shafts of the valve guides can wear out, leading to oil leakage into the exhaust gases. When this issue arises, your vehicle may start to emit bluish smoke from the exhaust pipe.

How To Fix Oil Coming Out Of Exhaust

When you observe engine oil to come out of the exhaust, it is important to take quick action. Follow the below-given steps to fix the oil coming out of the exhaust:

1) Remove Oil Cap

Please exercise caution while removing the oil cap with the engine operating, as hot oil may spray. Your objective in performing this job is to check the crankcase pressure. In a normally functioning engine, a minor amount of air should blow out of the filler cap due to pressure.

If you observe extreme air blowing out or detect a gas smell, it may indicate other problems like worn piston rings or a clogged PCV valve, resulting in a condition called engine blow-by.

2) Check Turbocharger

There are many methods to inspect the turbocharger, but the simplest method is through a visual inspection of the turbo impeller for a sign of oil leakage. This should be done for both the intake and exhaust impellers. Additionally, you may disconnect the hose from the intercooler and check for oil presence.

Feel the impeller for any wobbling or movement and examine the intake and exhaust impellers for any external damage, as it could indicate a faulty turbocharger bearing leading to oil leakage.

3) PCV Valve Cleaning

As discussed above, a clogged PCV valve is one of the major reasons for the engine oil to come out of the exhaust. This valve is usually mounted on the intake manifold.

To check this, simply remove it from the valve cover while keeping the hose connected. Place your finger over the open end of the valve and check if it creates suction. If it suctions, it means that your valve is working properly. If not, it needs cleaning.

Follow the below-given steps to clean the PCV valve:

Park your vehicle in a safe area.
Turn off the engine and allow it to cool down.
Disconnect the PCV valve.
Clear away any contaminants by using a carburetor cleaner or brake cleaner.
Use a compressor to blow air through the valve to remove any remaining dirt.
After cleaning, install the PCV valve back in its original place and check if it functions properly.
If your valve is still not working, you need to replace it.

4) Perform A Leak-Down-Test

Performing an engine leak-down test requires additional time and specialized tools, but it provides valuable insights for diagnosing issues. Follow the below-given steps to perform a leak-down test:

Ensure that the spark plugs are removed and position the cylinder you wish to test at the top dead center.
Try to attach the spark plug adapter with the gauge and insert it into the spark plug hole.
Attach the compressed air source while turning the regulator anticlockwise.
Pressurize the cylinder by turning the regulator clockwise.
Note the leakage percentage for each cylinder.

If the leakage percentage for each cylinder is according to the manufacturer’s specifications, follow the below-given steps:

Remove the radiator cap, oil filler cap, and oil dipstick.
After removing the air cleaner and opening the throttle body, listen for any escaping air.
The location from where the air is leaking is the cause of the issue.

5) Contact a Mechanic

If you encounter difficulties in fixing the problem, it’s advisable to seek assistance from a professional mechanic. They can provide expert help and prevent further engine damage.

How to Prevent Oil to Come Out Of Exhaust?

Follow the below-given measures to prevent oil from coming out of the exhaust:

Ensure the proper maintenance of your vehicle according to the vehicle manufacturer’s instructions.
Always use the correct type and viscosity of engine oil as suggested by the manufacturer.
When you observe a warning sign or warning light, immediately stop the vehicle and fix the issue.
You should avoid aggressive driving because it may also lead to oil leaks.
When you observe an engine issue, such as unusual smoke from the exhaust, poor engine performance, rough idling, or extreme oil consumption, contact a professional mechanic as soon as possible.
You shouldn’t overfill your engine with oil.
When changing engine parts or gaskets, ensure their proper installation.

FAQ Section

Can oil leak out of the exhaust manifold?

Yes, oil may leak out of the exhaust manifold gasket when it becomes old and worn, especially if there are problems with the engine. But if oil leaks around the exhaust manifold, there are chances that the oil is coming from the valve cover gasket above.

Can oil leak from an exhaust catch fire?

Yes, an oil leakage from the vehicle’s exhaust may ignite and cause a fire. The hot tailpipe may ignite the engine oil if the leak is significant. However, such incidents are very rare and generally happen when the leakage of oil is large. To prevent the risk of a fire, it’s crucial to promptly repair the oil leak found in your vehicle.

Why does my car exhaust smell like burning oil?

There are various mechanical issues that may cause engine oil to come out of the exhaust. Possible reasons include failed piston rings, turbocharger failure, a cracked engine block, faulty valve seals, a blown head gasket, damaged pistons, or a clogged PCV valve. Identifying the specific issue will require proper diagnosis by a qualified mechanic.

Why is there black liquid coming out of my exhaust?

Regarding the black liquid residue, it’s normal for exhaust systems to expel a small amount of water due to condensation within your vehicle’s engine. When this water blends with carbon deposits that naturally accumulate on the exhaust with time, it can give the appearance of a black liquid residue.

Why is my oil leaking on my exhaust and smoking?

As the motor oil of your vehicle starts to leak into the engine cylinder, it combines with the fuel-air mixture during the combustion process. This mixed oil is expelled from the exhaust pipe along with the combusted air-fuel mixture, resulting in bluish-white or white smoke. This is problematic because oil should not be present in the engine cylinder and can indicate a mechanical issue that needs attention.

Is it safe to drive when oil is coming from the exhaust?

If you notice oil coming out of the exhaust, it’s essential to have the vehicle checked promptly. It is not recommended to drive with oil coming out of the exhaust. This issue can indicate a significant issue that may worsen with time. Addressing it early can prevent further damage and costly repairs, whereas neglecting it could lead to severe consequences, even requiring engine replacement.

Why is my car running rich?

When an excess amount of fuel is injected into the engine cylinder, and there is an insufficient supply of air, the engine is said to be running “rich.”

Can oil catch fire on exhaust?

During hard braking, the oil leaks have the potential to fall onto the exhaust manifold, leading to a risk of catching fire. This fire can spread to a plastic spark plug wire channel and other parts of the engine. It’s essential to be cautious and promptly address any oil leaks to avoid such hazards.

What is the difference between engine oil leaks and oil coming from the exhaust?

An engine oil leak occurs when oil seeps from the engine and spreads into its surroundings. This can happen due to various reasons, including a damaged gasket or a fractured exhaust manifold. On the other hand, when oil spills from the engine and enters the exhaust system, it is commonly known as oil coming out of the exhaust.

Written By

Engineer Rahela

Rahela is the owner and main author of Mechanicalspecial. She is an automotive expert writer. She have over four years of experience in the automotive writing niche and have completed over 700 pieces of content from 40 projects. She have good knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance.