How To Read Spark Plugs Color To Analyze Their Conditions!

Knowing the condition of your spark plugs by reading

The spark plug in the car engine plays a vital role when it comes to producing a sufficient spark for the combustion of the air and fuel mixture.

Unlike what many car owners know is that the spark plug can be examined to figure out the general health or rather the condition of the vehicle engine.

This will help realize whether a repair is needed early enough to avoid spending too much on more complicated repairs.

Do you know how to read spark plugs? The readings on the spark plugs can be derived on keenly monitoring the spark plug and comparing the one you have with a normal one.

If you are accurate enough, you will be able to point out a number of issues with spark plugs and plan an intervention early to prevent further damages.

You can read the abnormal signs on the spark plug that will indicate complications with the engine.

An abnormality with the spark plug does not merely show that it is damaged, but it is communicating other issues within the car engine that caused the anomaly on it.

Why Is It Important To Read Your Spark Plugs?

When you take your time and study the condition of the spark plug, you will be able to learn a lot about the state of the spark plug.

This is because the spark plug is one of the significant ways that will show the operating condition of the spark plug, simply because it is subjected to those same conditions.

It is essential to read your spark plugs simply because some of the issues with the car engine may not be easily pointed out.

Some complications can’t be described as distinct, and you may come to learn about them when it is too late.

At such a time, the repairs needed to be done might either be too costly, or the damage might even be too severe.

You can either read the color of the spark plug, the condition of the parts, the type of deposits, and whether it is wet or not. In each of the findings, you will need a variety of conclusions.

These conclusions will not only indicate the health of the spark plug, but they will have a complete detail about the condition of the engine of the vehicle.

As such, you should not take for granted the readings that you get from the spark plugs.

What Do The Readings And Signs On The Spark Plugs Indicate?

After removing the spark plug from the engine, you should start examining it to sign that you can read.

For a standard spark plug, it may appear to be brownish or have tan shades on the tip of the electrode.

It should not just maintain its original color as it was when you bought it, as this will show that it is not even producing a spark.

1. Carbon Fouling

This may be seen as either black deposits on the spark plug or even dry soot on the tip.

This is referred to as carbon fouling and is usually the case because of a fault in the components of the engine.

These may include an air filter that is not clean, driving at low speeds frequently, a rather rich air and fuel mixture in the combustion chamber, and if you often leave your car engine idling.

You will need to have the engine checked as this will make it less able to perform optimally.

2. Deposits Of Oil On The Surface Of The Spark Plug

These appear as black oily deposits on either the electrode of the spark plug or its insulator tip indicates that oil can access it, which should not be the case.

This may mean that the pistons or the valves that need to prevent the passing of oil to the combustion chambers are slightly worn out, and that is why they are letting the oil into the cylinders.

You need to get an expert to examine this situation and figure out the source of the leak. Otherwise, every time you replace the spark plug, it will not be able to work as needed.

3. The Wetness Of The Spark Plug

This may indicate that the engine is firing because you try to start it, and it fails to fire up much often. This can be solved by drying the spark plugs before installing them back to the vehicle engine.

4. The Spark Plugs Appear Burned

If you notice a number of blisters on either the insulated tip, that the electrodes appear melted, or there are white deposits on the spark plug, then they are being subjected to too much heat.

This will indicate that the engine overheats much often, improper ignition, a spark plug that is not fitted tightly enough, or the spark plug in use is not of the correct heat range or the air and fuel mixture might just be too lean.

5. Pre-Ignition

Pre-ignition or detonation can be figured out by checking on the condition of the white porcelain. If you notice small dark specks or spots that appear as shiny, then the issue might just be pre-ignition.

This is usually caused when a part of the air and fuel mixture in the combustion chamber explodes instead of burning.

This will be heard as a knock sounds if you are keen enough.

This will significantly affect the condition of the pistons and also change the rings that are included to prevent the passing of oil to the ignition chamber.

This will then be followed by small amounts of fuel getting to the combustion chamber, where they should not be in the first place.


Now you know how to read your spark plugs. By reading your spark plugs, then you will know the condition of them.

You will see below are the questions that are often asked by the searchers who looked for the same information as you do. Keep reading the rest!

Q1. What Are My Spark Plugs Telling Me?

When you are keen enough and read your spark plugs every once in a while, you may be able to understand the condition of your car at a specific time.

This will prevent the car’s disease from worsening, and this will save you a lot of money when it comes to repairs that, at times, turn out to be quite costly.

Just in case, here are the top-rated spark plugs if yours are needed to be replaced.

For instance, if it appears oily, then the issue might be that the oil is getting past the faulty valve and into the combustion chamber.

Another issue that might communicate to you a problem with the car might be when you notice the spark plug is rather too wet-it indicates that the spark plug is not firing as needed due to flooding in the engine or that the ignition cable is faulty.

Q2. How Do I Know If My Spark Plugs Are Rich Or Lean?

Dark coloring and highly wet deposits on the spark plug may indicate overly rich conditions for the spark plug.

When the spark plugs show any signs of overheating, then they might be in rather lean conditions.

The spark plug appears burnt if the air and fuel mixture is simply too slim. If either is the case, early intervention is recommended to protect the integrity of the spark plug.

Q3. What Do Spark Plugs Colors Mean?

The spark plug on your engine should be either light brown or having deposits that are tan in color. These are the colors for a spark plug that is in reasonable working condition.

However, if you notice that it turns to either color or has deposits of different colors on the tip of the spark plug, then this might indicate some complications affecting its normal working.

Such are the complications that would raise eyebrows when it comes to the health of the spark plug.

On the other hand, if you notice that your spark plugs appear to have a green color, then there might be too much oxidation in the vehicle engine.

This will lead to the gap of the spark plug being affected, and thus this will affect the normal functioning of the spark plug.

It may also get worn out at a faster rate because it will have to apply twice its reasonable effort to produce tan effective spark.

What Color Should Spark Plugs Be?

The spark plug should either be brown or having tan deposits on its surface. This is because as it works, it will be subjected to electrode erosion, which is quite normal.

However, if the spark plug does not show any color, then they may not be producing any type of spark at all. The spark plug can’t simply maintain its original color as it had when it was new.

What Does It Mean When My Spark Plugs Are Brown?

If you notice that the spark plug is brown, then there is no need for alarm. This is the color for a normal spark plug that is in good condition.

A color that you should be worried about is a yellow gaze that might be formed on the tip of the spark plug’s electrode.

This will inhibit appropriate conductivity, and the spark product will not be that effective. You need to clean such a spark plug with a cleaner, such as a brake cleaner. Here ‘s how.

What Does It Mean When My Spark Plugs Are Black?

If you notice that your spark plug appears black in color, then it may not be in good condition.

This may be because of a weak spark being produced or the case that there is too much fuel in the combustion chamber.

These may be caused by a number of factors that range from either a stuck choke, an improper carburetor setting, an injector that is leaking, the spark plug having a high resistance, or that the coil has a fairly low output.

Q5. What Causes Spark Plugs Overheating?

Overheating of the spark plugs can be caused by a variety of factors, most of which are of great damage to the spark plug itself.

These factors include pre-ignition, which occurs when the timing is improperly timed or when the air and fuel ratio in the combustion chamber is not as required.

You should avoid this as overheating makes the spark plug work twice as hard, and this makes it wear out at a relatively fast rate.

You will need to replace your spark plugs way often because the one that is installed gets affected with too much heat.

If you need to change your spark plugs then this DIY guide can help you!

Q6. What Causes Black Carbon On Spark Plugs?

The carbon fouling that appears as either black and dry soot on either the electrodes and the insulator tips may be caused by a number of factors.

These are always irregularities that can either be a dirty air filter when you drive at a low speed for longer periods, when the air and fuel mixture is too rich or that you leave your car idling for extended periods.

You will need to avoid either of the above factors so that you protect the integrity of your spark plug.

This is because the soot or carbon deposits on the spark plug limit the ability of the spark plug to work efficiently.


All in all, you need to check on the condition of your spark plug. This will be helpful to point out issues with the car engine that might not be so obvious.

They will also help you avoid spending too much on repairs that you might have prevented in the first place.


1. NGK Spark Plugs –
2. Champion Auto Parts –


Written by Kane Dan

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