White, Black, Blue and Grey Smoke From Car Exhaust - What is it & Why

Every car has exhaust smoke coming out when it is in use. Most of the time, this is barely noticeable, but if it is, you might have to worry. The reason may or may not be serious. Apart from exhaust smoke, sometimes, there could be smoke coming out from under the hood of your car, and while it may not be anything you need to panic about, it could also be the contrary?

What Does Car Smoking Mean?

Car smoking is when there's smoke coming out from your car – it could be from either your engine or your exhaust. Depending on where the smoke is coming from, and whether it is serious or not, there are different ways by which you can deal with a smoking car.


What Are The Reasons For A Smoking Car?

As mentioned earlier, your car could be smoking from different places, for different reasons. Here are a few reasons that could be why there's smoke coming from your car:

1. Leaking head gaskets

2. Defective coolant systems

3. Burnt electrical wires

4. Worn out pistons

5. Faulty fuel valves

While these may not be the only reasons for your car smoking, they are some of the common reasons.

Apart from that, the most common cause of smoke under the hood is small amounts of motor oil or other fluids, which are accidentally spilled, or happen to leak from a bad gasket or seal, onto a hot engine or the exhaust system. The other fluids may include engine coolant, power steering, brake and transmission fluid, even window washer solvent. While this smoke is usually harmless, it needs to be addressed as soon as possible, to avoid any serious repercussions.

On the other hand, if there's smoke coming from the tailpipe, or from beneath the hood, it usually means that there's either a mechanical or electrical failure.

There are also different kinds of smokes that come from various places, like different types of engine smoke, different types of exhaust smoke, etc.

Did you ever have any of the following doubts in mind:

1. Car smoking under the hood

2. Car heating and smoking from under the hood

3. Steam or smoke coming from the front of the car

4. White smoke coming from the exhaust

5. Blue smoke coming from the exhaust

If you have ever had these doubts, then read on to know what causes smoking in your car, and how you can possibly prevent it from happening in the future.

What Are The Different Types Of Engine Smokes?

A number of reasons can result in your car's engine smoking. Depending on the kind of smoke that is coming from your car, the reason for the smoke can vary.

1. Black Smoke from Car Engine

If you have ever observed black smoke from your engine, the following could be the possible factors why:

a) Damaged Fuel Pressure Regulator

As the name suggests, this is the part of the felling system that regulates the pressure of the petrol or diesel being fed to your car. It can either be found outside or inside your car, and if this happens to be your problem area, then it is highly likely that it would need to be replaced. Also, you will have to check if your fuel pump needs to be checked if this happens to be the case.

b) Faulty Fuel Injector

Petrol or diesel is injected to the engine as high-pressure mist by fuel injectors. They can either get clogged with dirt or low-quality fuel, or there could be leaks due to the wear and tear of seals. The best option is to replace the seals and injector, in such a scenario.

c) Blocked Inlet Manifold

A mixture of fuel and air is supplied to the cylinders in the engine, by the inlet manifold. A limited amount of this mixture is supplied to the combustion system, in case there's a blockage in the manifold. This can result in a cloud of dirty smoke. While this can be tended to at home, it's always best to get professional help.

d) Dysfunctional Carburettor

Older cars use carburettors, which are used to mix air and fuel. When this part is not functioning properly, meaning that it could be delivering excess petrol or diesel to the engine, there would be black smoke coming from your engine. It is best to deal with this problem at the earliest, as there would be a lot of emission from your car, and there would be a lot of fuel burning too.

e) Ignition Timing Off

During the combustion cycle, fuel must be ignited at the right time for it to burn properly. If the ignition timing is off, excessive fuel is burnt off, which results in clouds of black smoke in extreme cases. It is always best to get it looked at, by a professional, at the earliest.

By making sure that none of the above problems occur, black engine smoke can be avoided at all costs.

2. White Smoke from Car Engine

Is white engine smoke coming from your car? The following could be the possible reasons why:

a) Cracked Engine Block

Engine blocks are those which keep all the major parts of your engine together. Extremely low temperatures can lead to coolant freezing and pushing against the walls of the block, causing small cracks. These cracks can result in white smoke from the engine. These repairs are often so expensive that it would cost much less to buy a new car instead.

b) Damaged Radiator/Coolant Hoses

Damages caused to hoses can be easily identified upon simply lifting the bonnet. Hoses to and from your radiator can collapse, swell or crack due to the passage of time. These are inexpensive to replace, and the process is better carried out by an expert.

Make sure that your engine block is intact, and that there's no damage done to radiator or coolant hoses, and you can prevent white smoke coming out from your engine.

What Is Car Exhaust Smoking and what Causes It?

As stated earlier, there is always smoke coming out from your exhaust. It is almost non-existent most of the time, when your car is in perfect condition. However, there can be visible smoke coming out from your exhaust, and this could be due to various reasons. And while smoke coming out of your car exhaust can be due to a less serious problem than when there's smoke coming out of your engine, you should always get your car checked in any case.

The reason for exhaust smoke can be determined by the colour of the smoke coming out from it.

1. White Smoke from Exhaust

If there's continuous white smoke coming from your exhaust, it could mean that there's some serious underlying problem, which could be the result of one of the following:

a) Cracked Engine Block

If there's a cracked engine block, it is almost impossible to repair it. it is vital for the running of your car and supports several key components. When there's a cracked engine block, the coolant can leak through the cracks and burn as white smoke. If there's a cracked engine block, it's better you replace the block entirely, but buying a new car is the most advisable option.

b) Blown Head Gasket

The head gasket keeps the coolant and oil from getting mixed up, by sealing the internal combustion process. When the engine is overheated, your gasket could be affected. This might result in the coolant flowing into the combustion chamber, which then evaporates as white smoke. You could try using a head gasket sealer to fill out small cracks, but more extensive damage will need the help of a professional.

c) Damaged Cylinder Heads

The combustion chamber is formed by cylinder heads that sit on top of the engine block. Overheating of these parts can cause your engine to misfire. When the air-tight seal is damaged, coolant can slip through openings and burn as white smoke. It is advisable to replace these cylinders than to repair them, as the heads must fit perfectly with the connecting parts.

2. Blue Smoke from Exhaust

Blue exhaust smoke can be observed during various situations, which can include any one of the following reasons:

a) Damaged Valve Stem Seals

The amount of fuel and air mixture allowed into cylinders for combustion is usually regulated by valves. The seals of these valves are made from high-strength rubber, but they can become cracked and worn out by extreme temperatures or by wear and tear. It is always advisable to get professional help for this problem.

b) Worn Pistons and Piston Rings

Rings help keep pistons keep an airtight seal on the cylinders of a combustion engine. When the rings have experienced some wear and tear, there can be oil leak into the fuel, which burns as blue smoke. While this is normally observed coming out of the exhaust, it can come out from the bonnet too.

c) Worn Engine Oil Seals

Several seals prevent oil from leaking from the engine. These seals can suffer from wear and tear, which results in leaks, which come out at blue smoke. Visiting a garage or a mechanic as soon as you notice this minimizes the problem.

d) Malfunctioning PCV Valve

A Positive Crankcase Ventilation valve releases exhaust gas and unburnt fuel from the engine block. If it malfunctions, it will mix oil, air and other gases inside the engine. This causes blue smoke. A PCV valve is usually replaced and doesn't cost much.

e) Head Gasket Failure

Overheating can damage head gaskets, which seal the internal combustion process. When there's a failure in this gasket, it can result in blue smoke. This repair requires professional help and might turn out to be quite costly.

f) Inlet Manifold Leaks

Fuel and air mixture is supplied to the cylinders in the engine by the inlet manifold. If the manifold leaks oil into the cylinders, this can burn as blue smoke. Getting professional help is the best option in this case.

3. Grey Smoke from Exhaust

If there is grey smoke coming out from your exhaust pipe, then it could be the result of any of the following underlying conditions:

a) Failed Piston Rings

If there's bluish grey smoke leaving your exhaust while your vehicle is accelerating, it could mean that your piston rings are damaged. The parts are found in cylinders and can leak oil when they lose their seal. This is a very uncommon problem and requires a professional to fix it.

b) Malfunctioning Valve Stem Seal

The valve in the combustion engines is lubricated by valve stem seals, which help maintain the correct ratio of fuel and air. Oil can leak when the parts become loose, or when the seal is lost. A professional is required to fix this problem, as it is complicated.

4. Black smoke From Exhaust

You can notice black smoke coming from your exhaust, due to any of the following problems:

a) Bad Fuel Pressure Regulator

A faulty regulator can increase the pressure of the fuel supply to the engine, due to which your car's fuel economy will suffer greatly. If excessive fuel is burnt, it can burn as black smoke, which is released through an exhaust.

b) Dirty or Clogged Air Filter

An air filter prevents unwanted debris from being sucked into your car's engine. Over time, contaminants collect in the filter, which clogs the filter and prevents it from working properly. Sometimes, the filter can also become damaged. If the debris happens to reach the combustion engine, it can be burned along with the fuel and result in black smoke. A filter replacement is enough to fix this problem.

c) Clogged or Leaking Fuel Injector

The objective of fuel injectors is to control to the amount of fuel delivered to the combustion chamber. If the injector delivers too much fuel, it comes out as black smoke. This is an indication that the part needs to be replaced.

Other Reasons to Smoke from Car

Is there smoke coming from your engine, but there's no overheating? This could be due to minor faults, but if left unchecked, these minor faults can turn out to be serious. These reasons can include:

1. Oil Filler Caps

A dark residue is left behind when fuel is burnt in some cars, and older engines especially are more susceptible to this problem, leaving behind a lot of smoke.

2. Leaking Coolant

The coolant overflow tank can leak fluid that burns and gives out smoke.

3. Oil Spillage

Make sure you use a funnel when refilling oil, as excess or leaked oil can result in the malfunctioning of parts.

4. Faulty Wires

A smoking wire is easy to spot, as it gives off a strong odour. However, it's difficult to spot the problem if it's coming from your alternator's copper wires, as the smell isn't as strong. Nevertheless, you can spot the problem as the engine lights turn on.

5. Oil Leaks

Oil leaks can take place anywhere, which can cause a lot of damage to the parts that the oil has leaked into.

How To Fix a Car That Smokes from The Exhaust?

Now that the basic understanding of what might result in the different colours of smokes coming from your car, here are a few hacks that you could try initially, to stop your car from smoking. You could always go to the mechanic if none of the hack's work.

1. How to Stop Black Smoke from Car

Sometimes, adding a complete fuel system cleaner to your gas tank could do the trick, as it will automatically clean injectors, carburettors, and intake valves. Sometimes, that's all you need to get your engine running cleanly again. If that doesn't do the trick, take your car to a mechanic.

2. How to Stop White Smoke from Car

Unlike a hack to stop black smoke, there's no hack or simple way of stopping white smoke from coming out from your car. Whenever there's white smoke coming from your car, take it to the nearest mechanic first.

3. How to Stop Blue or Grey Smoke from Car

Try adding a bottle of Motor Honey Oil Treatment to your motor oil with each oil change, as it is specially designed to reduce oil burning and stop smoky exhausts. If the problem persists, get professional help.


Smoke could be coming out of your car due to various reasons. And while not all of these are serious problems, even the most minor problems can turn out to be serious if left unchecked. As a result, it is always important to make sure that you tend to your car immediately, in case you see any smoke coming out of it. You can always fix the problem yourself, if it's something that can be done at home, or you can always take it to a professional and get the problem fixed. Getting a car warranty would come in handy at times like this, as your warranty would cover the repair expenses. Warranty Direct offers some of the best services to its customers. Head to our website to know more about our warranty policy.

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