White Smoke From Exhaust Smells Like Gas – Common Causes

In reality, the white smoke from exhaust smells like gas phenomenon is fairly popular. However, most car owners can’t recognize and determine the problem in the early stages.

It’s understandable because this phenomenon isn’t always huge at first. Moreover, people hardly can’t gauge the issue’s severity based on the fume’s types and colors.

But don’t worry! This post will assist owners experiencing this problem in understanding the phenomenon, the roots of the problem, and possible solutions.

Possible Causes Of White Smoke From Exhaust Smells Like Gas

White Smoke From Exhaust Smells Like Gas

There are many potential roots behind this white smoke that smells like gas. Some of them are condensation, internal leaks, broken head gaskets, faulty fuel injectors, worn valve seals, etc.

It’s important to remember that all of these causes are connected. All the components need to be linked to work together. Thus, if one part is broken, it may entail other symptoms and damage.

For example, a blown head gasket can lead to a coolant leak, leading to burning coolant smoke.

In reverse, when the coolant leak happens, the heat generated from the car operation can’t be handled well. As a result, the engine starts to overheat, which returns to damage the head gasket more.


We have to say that white exhaust fumes don’t always mean there’s a problem. Yes! In many cases, this white color comes from condensation.

The root of this chalky smoke is steam or vapor consenting in the exhaust pipe, leading to high humidity.

When we start our cars, the engine generates heat, and hot exhaust gas comes out, interacting with a high-humidity environment.

This interaction will lead to a white flow of smog. Moreover, we can see this phenomenon clearer if we’re in cold or high-humidity weather.

If we see white, wispy smoke during startup, especially on cooler days, and it soon goes away, it’s condensation.

Often, drivers in warm regions can be confused and concerned about white smoke when they move to areas with lower temperatures.

However, it’s nothing to worry about, as this kind of fume usually diminishes after a brief driving period. The interaction soon ends as the heat handles all the steam appearing in the exhaust.

Coolant Leak

One of the possible causes of milky smog is a coolant leak. After the warm-up process, the coolant may be internally leaking if we still see white smoke coming from the exhaust pipe.

Signs of this root are that we can see the white fume and feel a slightly sweet smell coming from it. Usually, the cylinder head can be cracked or worn, which is the most common cause of a coolant leak.

Even a little fracture might cause coolant to leak and then contaminate the car engine’s oil. This mixture of the coolant and oil will give the fume a milky color.

In worse cases, the engine will be overheated because of the low coolant level. Then, it might rupture the head gasket, which is also the next cause!

A Damaged Head Gasket

Another cause of white exhaust smoke is a damaged or blown head gasket.

Basically, the damage to the head gasket will allow coolant to enter the combustion chamber. However, the coolant is different from fuel.

The coolant will vaporize because it can’t be burnt and does not participate in the combustion process. As a result, similar to the previous concept, the exhaust will emit a lot of white smoke.

In this case, a broken head gasket will clean the combustion chamber as there is coolant fluid in it, but the cooling system is unclean.

Therefore, signs indicating a damaged head gasket are white smoke, a clean combustion chamber, and a dirty cooling system.

Oil Leak

Can low oil cause smoke exhaust white? – Yes! An oil leak can cause this color.

In most cases, this leak comes from the fractured piston rings that have been used for a long time or in an overheated environment.

This leak lets the oil penetrate the combustion chamber and combine with the fuel. Like the coolant, the engine oil doesn’t participate in the combustion process.

As a result, the mixture of oil and fuel will create a car burning oil white smoke.

It’s recommended to address this leaking problem as soon as possible. Otherwise, our car’s engine may suffer further damage.

Transmission Fluid Leak

Another leak that can also lead to white smoke from the exhaust is the fluid leak in the transmission system. We can determine this cause by noticing the acceleration process.

The more we press the pedal to accelerate, the more white smoke comes out. The exhaust may have an unpleasant gas or burnt oil odor in this situation.

Some of the common culprits for this transmission leak are old transmission pans, broken gaskets, or cracked fluid lines.

The engine will consequently start to deteriorate soon. So, bring our automobile to a mechanic so they can fix the leak to avoid additional damage.

Problems of Fuel Injectors

Can too much fuel cause white smoke? Yes! Issues related to fuel injectors can make our cars’ fumes become milky.

For instance, too much fuel will be delivered to the combustion chamber by a malfunctioning fuel injector, which usually is stuck or leaked from the O-rings.

The extra fuel cannot be burned correctly in the engine. In other words, that redundant amount reduces the efficiency of the combustion process, leading to a white or gray color fume at the end.

Honestly, identifying which fuel injector has a problem and needs to be replaced is a difficult task. It requires time and a certain understanding.

However, most mechanics will suggest replacing all of them to save time because they are low-priced.

Broken Catalytic Converter

Car burning oil white smoke may potentially be caused by a defective catalytic converter.

In this case, white smoke comes from the exhaust, and catalytic converter-related DTCs (diagnostic trouble codes) will be displayed on the dashboard.

A defective catalytic converter is also related to the leaks mentioned before.

For instance, a worn-out piston ring causes the oil to leak into the combustion chamber and then get up in the catalytic converter. In the end, our cars release white smoke through the pipe tail.

Piston Ring or Valve Seal Problems

The last thing we want to mention also connects to the above concept, the valve seal problems. This correlation is understandable as our car components must be connected to function well.

In this instance, faulty piston rings or seals allow lubricant to get inside the burning chamber, which combines with the gasoline and ignites.

As a result, white or light-bluish smoke emerges from the exhaust manifold.

What Should We Do If Met This Issue?

What Should We Do If Met This Issue?

First, it’s advised that we should stop driving our cars. The main reason is that we can save our engine from further harsh damage.

Then, follow the below steps to get the general fixing approach.

Step 1: Observe

Let’s take a look at the time when our cars emit white smoke. For example, if it only happens within a minute, it’s normal due to the condensation phenomenon.

If white or gray smoke occurs frequently and longer, it’s time to make further inspections.

Step 2: Check the components

We can start by examining the coolant level. Then, let’s look for any leaks. We can check with a chemistry device to find contaminants in the coolant and detect engine block leaks.

In the absence of coolant leakage, it’s possible to infer that our car has a broken or leaking head gasket.

We can do the whole checking process if we have enough necessary tools, knowledge, and skills. Otherwise, let’s consult a trustworthy auto repair for an accurate diagnosis.

These problems can be verified through the process, including taking apart the engine and reaching the block.

Step 3: Fix the malfunctioning

Once we realize that we have damage in any parts, we’ll need to fix it! Depending on the broken components, we can repair or replace them with new ones.

For example, if we have a burst head gasket or a jammed fuel injector, it usually requires a replacement.

Step 4: Re-check 

After fixing the problems, remember to re-examine the car’s status. Does the vehicle no longer produce white smoke? Has the exhaust smoke smells like gas gone? And other changes, if any.

Frequently Asked Questions

Why Does Your Exhaust Smoke Smell Like Gasoline?

If the combustion chamber has too much air, oil, or coolant leak, our exhaust smoke will smell like gasoline.

Coolant and oil enter the combustion chamber through leaks, where they are burnt partially. Therefore, car exhaust smoke has an unpleasant gas or even burned plastic odor.

Is It Safe To Drive With White Smoke From Exhaust?

No. Driving while a car emits white smoke is unsafe since further dangerous problems may appear.

For example, if the head gasket or the coolant leaks into the combustion chamber, driving an automobile with these problems will severely ruin the engine.

What Do Exhaust Emissions Normally Look Like?

Normally, the car emissions would be light white, pale gray, or even colorless. Therefore, we don’t usually recognize it.

However, if a car smokes when starting up with a white color happening for seconds, it’s also normal. Serious problems are mainly expressed through thick white smoke.


Generally speaking, when white smoke from exhaust smells like gas appears, there are multiple roots that we should check.

Let’s look at the coolant, head gaskets, fuel injectors, valve seals, etc. If there is a crack, we need to patch it right away.

Otherwise, the combustion chamber produces white smoke, and additional complications develop gradually in the car engine.

It’s ideal to call a mechanic to fix the problem if we cannot handle it ourselves.

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