Blue Smoke From Exhaust: Causes And How To Fix

During the operation of vehicles using internal combustion cars, the appearance of smoke is not something too strange. This type of by-product is a must-have result of the combustion of the fuel mixture inside the cylinder, which helps to create pressure and push the piston and the shaft to move.

However, we can only conclude that everything usually goes when the smoke from the exhaust is almost transparent or has a very light white color.

If the smoke has a color like black, gray-white, or especially blue, your car is having a problem. In today's article, I will show you the issues and how to fix them every time you encounter blue smoke from the exhaust.

Blue smoke from exhaust: What are the causes?

Your car is a homogeneous mass with dozens of different parts working together. So, we only consider the leading causes that often cause this problem.

1. Oil in the combustion chamber


Oil in the combustion chamber

One of the most common causes of the problem of white to blue car smoke is a leak of fluid inside the combustion chamber.

Typically, the fluid will move in locations utterly separate from where fuel and air mix and then come into contact with a heat source.

For some reason, if the piston rings, valve seals, and other holding mechanisms deteriorate, such as not receiving the necessary maintenance or these components are too old, the lubricating liquid will slowly move through the openings or cracks and enter the combustion chamber. The result of this leak is a layer of blue smoke that we can see with the naked eye or, worse, damage deep inside the engine.

The oxygen sensor will be damaged if lubricating oil gets into the combustion chamber and also causes the vehicle to lose a significant amount of oil.

2. Blown turbocharger


Blown Turbocharger

The engine turbocharger is a component that gives your engine a noticeable boost in performance. But this part is also the cause of the car's blue smoke emission.

Because when operating, the turbocharger will work with high-intensity compressed air, and if this air flow does not move following the design, the damage will occur, and the consequences will be a rather large hole. 

From this leak, engine fluid or coolant can get inside the engine while fuel combustion occurs, which produces blue smoke from the exhaust.

3. Broken piston ring

To separate liquids such as engine oil from other parts of the engine, manufacturers have used thin piston rings to eliminate the possibility of leaking even a small amount of liquid. However, every detail has a lifetime, and so do these piston rings.

Under unfavorable operating conditions or not receiving the necessary maintenance, the service life of this metal part will be greatly reduced.

When the rust has spread too widely, the ring is not strong enough to keep the oil from flowing back into other parts. And when this engine oil mixes with the fuel, blue smoke will appear.

4. The PCV valve is stuck


PCV valve is stuck

If oil leaks into the combustion chamber or other combustion processes is already a terrible thing, then oil leaking directly into the fuel or fuel compartment will create blue smoke and have consequences later.

But why can fluid get inside the tank and the fuel line? Here we will have some main reasons as follows.

Valve seals, piston rings, and PCV valves can no longer function properly. With valve seals or rings, leakage will depend on the location where the part is damaged.

The PCV valve uses the engine's vacuum to suck out any remaining air in the crankcase, then pushes all of this gas into the intake manifold and into the combustion chamber where it is re-ignited.

When the PCV valve is stuck if it is too degraded, this time, the fluid will mix with the air and other gasses and mix with gasoline, leading to blue smoke from the exhaust.

5. Oil dripping on engine

Like many other liquids, the oil will evaporate as soon as it gets too hot. 

During the move, if this oil accidentally leaks and falls into any part of the running engine and has a surface with a temperature of up to hundreds of degrees, the evaporation reaction will be immediate.

The result of this process is blue smoke.

For more causes, check this video:

Video created by Auto Repair Guys

Blue smoke from exhaust: How to fix

1. Remove excess oil

As mentioned above, one of the causes of blue smoke from cars due to oil problems. So affecting the amount of oil inside the vehicle will be the optimal method to deal with this problem quickly.

You will first need to remove excess oil to avoid excessive pressure damaging the pipes or increasing the risk of leaks.

The more excess oil, the more likely it is that aeration and pressure increase will occur.

If too much oil is poured in, the excess oil will not have room to circulate. When the engine is running, the shaft will rotate and the excess oil will be mixed with the air causing aeration. Oil has air bubbles, the lubricating ability will be reduced, causing the machine to heat up. Gradually, it will lead to damage to the details in the car's engine.

In addition, excess oil will create excessive pressure inside the engine and will find its way out through various rings and seals. If one or more of them fails, that will lead to leaks and costly repairs.

The result of these two phenomena is to make it harder for the engine to handle heat and friction better. Simply remove the excess oil and keep only enough oil at the required level to solve this problem.

In addition, removing excess oil can also help remove old fluid that can no longer protect components from friction.


2. Clean the engine

Engines that are not cleaned and maintained regularly will quickly deteriorate and eventually create leaks and cause blue smoke. Maintenance in general and engine cleaning, in particular, will significantly prevent or even end this problem.

3. Replace broken piston rings

If the piston rings are worn, it will cause the engine lubricating oil to go up to the combustion chamber and be burned, reduce the efficiency of the engine, and cause blue smoke in the exhaust.

So, piston rings provide sealing of joints, ensure no oil leakage, and have many other capabilities and benefits. Therefore, it is necessary to check and remove damaged rings and replace them with new ones.

4. Replace the new PCV valve

The PCV valve is an important part of the exhaust system, so if the PCV valve is clogged or stuck, it will prevent air from entering the intake manifold and being discharged to the outside. Therefore, when seeing signs of a damaged PCV valve, it is necessary to take the vehicle to the repair and maintenance center to replace the new valve.

Cost of Fixing 

The cost of fixing a blue smoke problem will depend on where the problem is coming from within the vehicle's system.

If you are lucky, you'll only have to replace the $40 valve cushions and a few tools to manipulate. If you are not sure about your ability, it will cost you between $100 and $600 to a professional shop for inspection and replacement.

In the worst case, the car's piston ring will be damaged, and the cost to repair it will be $1000. It is often difficult to access this position, and fear of repair will have to disassemble the entire engine block to operate. Sometimes you will even have to replace your engine at up to $7000 or more.

Frequently asked questions (FAQs)

  • Can a PCV valve cause blue smoke?

Yes. When the PCV gets stuck and does not open and close at the right time, the oil mixture with air and other gasses will take place continuously inside the engine. The combustion of this mixture will cause blue smoke.

  • Does synthetic oil burn blue smoke?

Synthetic oil can still cause blue smoke if leaked to the outside. However, you can consider using this oil because of its stable quality and its ability to block smoke effectively.

  • Can overfilling oil cause blue smoke?

Indeed, too much oil inside the car will cause tremendous pressure, leading to blue smoke formation.


I have provided you with the causes and how to fix blue smoke from the exhaust, essential information to ensure your car always works at its best. Hopefully, today's knowledge will bring you many impressive benefits.

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