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Why Is Blue Smoke Coming From the Exhaust? (Explained)

Updated: Jan 9

Exhaust smoke is a common sight on the road, and it can come in a variety of colors. White smoke is generally caused by water entering into the exhaust, while blue smoke indicates an issue with the engine, usually oil leaking into the exhaust.


Blue smoke from the exhaust is a sign of an oil leak in the engine. Have the vehicle checked for issues like leaking valve seals, damaged piston rings, or worn cylinder walls. Continuing to drive with an oil leak can cause further damage to the engine.


In this article, we'll take a closer look at the causes of blue smoke from the exhaust, as well as some possible solutions for fixing it.

 

Table of Contents:


smoke coming from a car exhaust tip

Causes of Blue Smoke From the Exhaust

There are a few different reasons why blue smoke might be coming from your exhaust. Some of the most common causes include the following.


  1. Worn Valve Seals: The valve seals in your engine help to keep oil from leaking into the combustion chamber. If these seals are worn or damaged, oil can leak into the chamber and burn along with the fuel, creating blue exhaust smoke.

  2. Worn Piston Rings: The piston rings in your engine help to seal the combustion chamber and prevent oil from leaking into it. If these rings are worn or damaged, oil can leak into the chamber and burn along with the fuel, creating blue smoke.

  3. Clogged PCV Valve: The PCV (positive crankcase ventilation) valve is a small valve that helps to regulate the pressure in the crankcase of your engine. If this valve becomes clogged, it can cause excess oil to burn in the combustion chamber, causing blue smoke to come out of the exhaust.

  4. Oil dripping onto the exhaust: Sometimes an oil leak can cause oil to drip and leak onto the exhaust system, this is most common on the exhaust manifold. It will typically cause blue smoke to exit the vehicle, usually in the engine bay and not from the exhaust.

  5. Oil dripping onto hot engine components: Sometimes an oil leak can cause oil to drip and leak onto hot engine parts such as the block. It will typically cause blue smoke emit from the vehicle, usually in the engine bay and not from the exhaust.

  6. Bad glow plugs (diesel vehicles): Sometimes faulty or worn glow plugs can cause blue smoke to emit from the exhaust.


Blue Smoke Coming From the Exhaust When Accelerating

If you notice blue smoke coming from the exhaust only when you accelerate, it could be a sign of a problem that becomes worse as you accelerate. Sometimes the extra pressure within the engine from higher rpms and boost pressure causes more oil to enter the combustion chamber.


Faulty valve seals, piston rings and PCV valve will allow more oil into the engine as the rpms increase, causing more blue exhaust smoke during acceleration.


Blue Smoke From Exhaust on Startup Then Goes Away

If you see blue smoke from the exhaust only when you start your vehicle, it could be a sign of a problem with the valve seals or piston rings. As the engine warms up, these seals and rings may expand and seal properly, which could cause the blue smoke to disappear.


Does Blue Smoke Mean Blown Head Gasket?

A blown head gasket can cause blue smoke from the exhaust, but it's not the only possible cause and is more likely to cause white smoke from the exhaust.


Other issues, such as worn valve seals or piston rings, can also cause blue exhaust smoke. It's important to have the problem properly diagnosed by a mechanic in order to determine the root cause and choose the appropriate repair.


Can Wrong Oil Cause Blue Smoke?

Using the wrong type of oil in your engine can cause blue smoke from the exhaust. For example, using an oil with a higher viscosity (thickness) than recommended by the manufacturer can cause excess oil to burn in the combustion chamber, creating blue smoke to come from the exhaust.


It's important to use the correct type of oil as specified in the owner's manual. Overfilled engine oil can also cause blue smoke to come from the exhaust, it's important to only fill the engine oil up to the right amount.


engine oil being poured into an engine

How to Fix Blue Smoke From the Exhaust

The best way to fix blue smoke from the exhaust is to diagnose and address the underlying cause. This may require the help of a mechanic, who can use specialised tools and diagnostic equipment to pinpoint the problem.


Some possible repairs for blue exhaust smoke include the following.


  1. Replacing worn valve seals or piston rings: If the problem is caused by worn valve seals or piston rings, these parts will need to be replaced. This is a complex repair that should be performed by a professional mechanic.

  2. Cleaning or replacing the PCV valve: If the PCV valve is clogged, it may need to be cleaned or replaced. This is a relatively simple repair that can usually be done by a mechanic or even a DIY enthusiast.

  3. Replacing faulty glow plugs: If the problem is caused by faulty glow plugs, these parts will need to be replaced. This could be a more complex repair that should be performed by a professional.

  4. Fixing any oil leaks: If the problem is caused by an oil leak, such as oil leaking onto the exhaust manifold or headers, it will need to new repaired.


Can I Drive With Blue Smoke Coming From the Exhaust?

It is not recommended to drive a vehicle with blue smoke coming from the exhaust. This is a sign of a serious problem with the engine, and driving the vehicle could cause further damage.


It's important to have the problem properly diagnosed and repaired as soon as possible to avoid further issues and costly repairs.


Conclusion

In conclusion, blue smoke coming from the exhaust is a serious issue that should be addressed as soon as possible. There are a variety of possible causes for this issue, ranging from worn valve seals, worn piston rings or even faulty glow plugs.


The best way to fix the problem is to have it properly diagnosed and repaired by a professional mechanic. In the meantime, it's important to avoid driving the vehicle to prevent further damage.