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Blue smoke from the exhaust (causes and how to fix it)

A car exhaust can tell you a lot about the condition of your vehicle. As long as everything is working optimally, the exhaust should sound like a thin white or very light cloud of water vapor. If you notice blue smoke coming out of your exhaust, it’s a sign that something is wrong.

We review some of the main causes of blue exhaust smoke. Our article also gives you some practical tips to solve the problem once and for all.

What is blue exhaust smoke?

Blue smoke is produced when oil mixes with gasoline in the combustion cycle. It can also be caused by oil dripping on hot engine parts. In some cases, blue exhaust smoke is a sign that a part is failing, such as the turbocharger or PCV valve.

When there is blue smoke, it means that the oil is burning and is coming out of the exhaust pipe along with the burned fuel. Whatever the cause, the vehicle is running inefficiently and needs repair.

Blue smoke from exhaust causes

1. Oil in the combustion chamber

combustion car

As the engine ages, piston rings, valve seals, and other vital components begin to wear out. Wear occurs faster if you don’t perform regular oil changes because contaminated oil is less effective at reducing friction.

If valve seals crack and break, fluids are less likely to stay separated. This is when the oil begins to mix with the fuel in the combustion chamber.

Blue smoke coming from the exhaust often indicates that there is oil in the combustion chamber. Sometimes this is due to worn piston rings, which means the engine may need to be replaced.

RELATED: Black Exhaust Smoke: Causes and How to Fix It

2. Turbocharger blown


If the turbo has blown out, there is a possibility of blue smoke coming out of the exhaust. A blown turbo can mean it’s damaged, but it can also be caused by a leaking oil seal.

In both cases, oil leaks into the engine. After the oil seeps into the engine, it mixes with the fuel to create blue smoke.

3. Damage to the piston rings

Piston ring function

Piston rings are created to keep engine oil in place in the combustion chamber. When they fail, oil can leak into the wrong area.

When oil mixes with fuel, it can create blue smoke. Unfortunately, replacing piston rings can be very expensive.

RELATED: 4 Symptoms of a Bad Piston Ring

4. Oil drops


If something is wrong with the vehicle and hot engine oil is leaking, it can come into contact with hot parts under the hood. When accelerating, you may notice blue smoke coming from the rear of the car due to the oil hitting the engine block. Although it’s not actually coming from the exhaust, it might seem like it.

Oil may drip from a blown gasket in the engine block. As it infiltrates, it makes its way to the hot exhaust, resulting in blue smoke. Additionally, it could leak into the headers, also causing blue smoke.

If smoke comes out from under the hood when you’re not driving, it’s a telltale sign of an oil leak. Unfortunately, when the head gasket leaks, you may also need to replace a cylinder head.

5. Blocked PCV valve

PCV valve

The positive crankcase ventilation (PCV) valve can also generate blue smoke in the exhaust. This valve is responsible for releasing pressure that builds up in the oil pan. The pressure is directed to the intake manifold, so the fumes can be burned off again.

When the PCV valve is stuck, oil mixes with air and other gases. Since the intake manifold is also connected to the air filter, this can cause blue smoke.

RELATED: 7 Symptoms of a Bad PCV Valve

How to fix blue exhaust smoke

1. Remove excess oil

The simplest solution is to remove the oil from the system. This solution only works if the blue smoke occurs directly after performing an oil change.

There may be too much oil in the system. This condition causes aeration and pressure, making it difficult for the engine to properly handle heat and friction. To fix this problem, remove enough oil so that the levels are correct.

RELATED: White Exhaust Smoke: Common Causes and How to Fix It

2. Clean the engine

If the engine hasn’t been cleaned in a while, it’s time to take a look. When dirt gets stuck in the engine, it can clog the oil return holes in the cylinder head and cause a leak.

Remove the valve cap and clean up any debris you see. You also want to clean the drain holes. Clean the engine to make sure there is no oil left that could cause blue smoke.

When you clean the engine, it’s a good time to inspect it. If you notice an area where there could be an oil leak, fix the problem immediately.

3. Replace piston rings

Damaged piston rings can cause blue smoke, but it’s not an easy problem to fix. While piston rings only cost about $50 each, it’s the labor that makes the bill so high.

The motor must be removed and disassembled to access the rings. Expect to pay $1,000 or more until all the work is completed.

4. Repair the turbocharger

If the turbocharger burns out, you should stop driving immediately. Driving a car with a blown turbo can lead to much bigger problems.

In fact, pieces of metal can form because there is no lubrication in the turbocharger. This metal can enter the engine and cause permanent damage.

5. Replace the PCV valve

Replacing the PCV valve is inexpensive. Plus, the work is simple. Identify the tube that connects from the intake manifold to the valve cover and follow it until you find the PCV valve.

Remove the valve and replace it with a new one. As long as you put the new valve in the right place, everything will work as it should, hopefully fixing the blue smoke condition.

6. Repair of valve seals

Unless you have some mechanical knowledge, you don’t want to try to repair valve seals yourself. You’ll need special tools and a little finesse to get the job done right.

To replace the valve seals, you must remove the rocker arm spring and valve. Lift the valve seal and replace it with a new one. Whatever you do, don’t drop the engine valve, or you’ll have bigger problems on your hands.

Driving with blue exhaust smoke

In some cases, it is normal to continue driving with blue smoke coming out of the exhaust. However, you want to make sure you know what the problem is before making it worse. If the turbocharger is burned out or oil is mixed with the fuel, you should stop driving and fix the problem.

Letting problems continue only increases expenses later. If you need to replace an engine due to damage, the cost can be $3,000 or more, which you don’t want to deal with.


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