Blue Smoke From Exhaust

The appearance of blue smoke from the exhaust pipe comes as a complete surprise to many drivers. Especially if it happens for the first time. Looking ahead, we will immediately say that this is a consequence of getting engine oil in the engine cylinders. What are the causes of this, and what is worth doing to eliminate the problem? We will tell in detail in the article.

Why is smoke coming from my exhaust?

Usually the amount of smoke is greater in wet weather, so deviations in its color and impurities are easier to notice then. The color of «blue» smoke can be different. Starting with blue and ending with a thick rich blue. However, in any case, its oily nature is a characteristic feature. That is what allows you to determine the cause of the appearance.

Such smoke is poorly dispersed in the air, and in its composition there are greasy droplets that literally fly out of the pipe together with the gases. Unlike white smoke, which is caused by the appearance of coolant in the cylinders, blue smoke tells the car owner that oil gets into the combustion chamber.

At the slightest suspicion of blue smoke coming from the exhaust, it is necessary to measure the oil level in the engine.

What are the consequences of running the engine when the car smokes blue?

In addition to the direct appearance of blue smoke from the exhaust system, there are a number of other indirect signs indicating that oil is getting inside the cylinder:

Black soot on the spark plugs is the main sign of oil in the cylinder

  • The engine «jerks» (runs unstable);
  • the level of engine oil consumption increases significantly (up to 1 liter per 100 kilometers);
  • quick failure of spark plugs (they are covered with black sludge);
  • decrease of compression value in one or several cylinders;
  • there may be problems with starting the car in cold weather;
  • presence of burning smell in or around the car.

How oil gets in cylinders

Most often (but not always) oil enters the combustion chamber in one of two ways, specifically through:

  1. piston rings;
  2. the gap between the valve pins and the guide sleeves;
  3. problems with the turbine (on turbocharged engines).

What are the causes of oil in the engine cylinders?

Significant wear of the valve caps

Depending on the signs, intensity and when the blue smoke starts, you can easily determine the cause of the malfunction. These include:

  • Complete or partial depressurization of the valve;
  • considerable wear or failure of the valve cap;
  • scratches on the cylinder surface;
  • defects in operation of piston rings;
  • changes in the geometry of one or more cylinders.

Below we will consider how to determine some of the described situations.

How is it diagnosed?

When the valves are burned or leaky (due to a large amount of carbon deposits), the smoke becomes white-blue. It is not difficult to determine the fault. For this purpose, you need to measure the compression. It will be insignificant or absent at all.

When the oil caps are blistering or cracking, the amount of oil entering the cylinders increases at idle and during engine braking. During this time there is a high vacuum in the intake manifold. This results in a large pressure differential and the oil seeps into the cylinders and builds up on the walls in the exhaust system. The moment the throttle is opened, the blue smoke with oil gets thicker. If you see blue smoke at startup but goes away, the oil caps have started leaking oil.

When there is bluish smoke from the exhaust pipe of a new car when warming up, and then the smoke disappears, do not worry — it is lapping parts.

To see the defects on the cylinders or pistons, you have to disassemble the engine as the smoke will go on and on. The only sign that can be seen (when changing the oil or testing the engine oil) is a metallic slurry in the oil.

Corrosion on the rings or cylinders

When scuffing occurs, there is a depressurization and oil enters the combustion chamber under the rings. Causes of the flaws may include:

  • The presence of abrasive particles in the oil. This can be due to poor oil quality, a clogged filter, or significant machine mileage without an engine oil change.
  • Corrosion on the rings or cylinders. It can occur due to a variety of causes. One of the common ones is long parking of the car in the open air without starting the engine.

If the piston rings are lodged, blue smoke from the exhaust pipe appears when the car accelerates. If you check with a compressometer, you can notice both a decrease in compression, in the problematic cylinder, and vice versa an increase. Also the work of the crankcase gas ventilation system is disturbed.

If the appearing gaps in the case of an engine cylinder piston group malfunction are small, then there is a chance that the compression value will be high, as the incoming oil will gradually seal them.

If poor quality oil is used, the rings may burn in or lodge in the piston grooves. The rings may also be crimped at the seating points due to long glow ignition. In this case, they are completely immobilized.

Usually the defects described above do not occur in all cylinders, but only in one or more. The easiest way to start the diagnosis is to assess the condition of the spark plugs, as well as to measure the compression level.

Worn turbocharger rotor components

If your car engine is equipped with a turbocharger, there may be another reason for the blue smoke coming out of the exhaust — the seals and bearings of the turbocharger rotor are worn. If the turbine seal is damaged, diagnosis is difficult because the oil gets into the exhaust system, where it burns off. To diagnose this, simply remove the turbocharger intake manifold and look inside. If the seal is damaged, you will see a puddle of oil.

If your car has an automatic transmission (automatic transmission), smoke with a bluish tint can occur due to a failure of its regulator diaphragm in case there is a vacuum load cell. You can diagnose such a malfunction by significant sooting on the spark plugs. You can easily recognize the oil, as transmission fluid for automatic transmission has a reddish or yellow color and specific smell.

How do you fix blue smoke from exhaust?

Before resorting to repairing the engine, according to the symptom and the specific cause to get rid of the smoke or significantly reduce the intensity, you can try using the additive in the oil (to restore the performance of drain plugs) or making anticlocking of the rings (if they lie), but in most cases, you still need to replace the defective part or repair the engine.

ReasonHow to determineWhat to do
Wear of valve oil sealIntense smoking when starting the engine (especially noticeable when the engine is cold)Replace the valve seals, but you can try to use an additive in the oil to restore their performance
Valve burnout or heavy fouling
  • There is a bluish smoke all the time, but in small quantities.
  • The engine will not run steadily.
  • When you check the compression in the cylinders it will be determined which one will be much lower than the others.
Disassembly of the valve, cleaning and lapping or complete replacement of the defective valve
Defects in the condition of the cylinders
  • Metal dust in the engine oil.
  • Reduced engine power.
  • Reduced compression in cylinder.
Cylinder turning or replacement of the block liner
Piston ring lodging
  • Smoking on acceleration, at high rpm.
  • Compression level deviates upward or downward.
  • Crankcase gas ventilation is disturbed.
Fix a stuck piston rings or replace the rings, having previously cleaned the grooves in the piston.
Wear of bearings and seals on the turbine rotorOil in the intake tractReplace defective parts or repair the turbine


There are not many reasons why there is blue smoke coming out of the exhaust pipe. As a rule, problems occur with oil caps, rings, cylinders. Remember that it is possible to use the car in this case, but it is not desirable, because such engine operation leads to the increased consumption of fuel and oil, and also to the loss of capacity due to the increase of a layer of soot on the valves. If it is necessary to use the car, it should be done with care, avoiding considerable loads on the engine. In fact, operation in such conditions wears out the already «tired» engine and brings closer the time of its overhaul. Therefore, when the smoke is blue do not delay diagnostics and repair work. Often a timely replacement of penny oil caps will be able to prevent expensive repair of more complex nodes of the engine of the car.


  • What does blue smoke from the exhaust pipe tell you?

    It tells about an oil leak and that the engine of your car is burning oil. Probably the piston rings are logged or the turbine needs repairing.

  • Can you drive with blue smoke from exhaust?

    You can drive with blue smoke from exhaust, but remember, it's the signal to visit the service station and show your engine to a qualified mechanic.

  • How much does it cost to fix blue smoke from exhaust?

    The price depends on the nature of the damage: valve seal — approximately $40, main parts — $80, labor cost — $300, engine replacement — $2500.

Ask a question
Is the article useful? Yes No
See also
Can't find an answer to your question?
Ask in the comments. We will answer for sure!
Loading comments