Why Are My Spark Plugs White? – Reasons and Solutions

We all know the importance of spark plugs in a combustion engine. If it is okay, it will ignite the air-fuel mixture well. Otherwise, if it becomes defective, it may cause multiple issues. Thus, I am here to discuss a severe problem with spark plugs. You probably already found it and questioned – “why are my spark plugs white?”

 When functioning optimally, the spark plug shows a light brown or grayish-tan color (1). It may indicate different issues if you find it coated in a white, powdery substance. It may refer to abnormal combustion temperatures, engine overheating, or intake manifold leaks (2,3,4). Again, it may also happen due to low fuel pressure, poor quality fuel, incorrect ignition timing, or worn-out spark plugs.

Well, you may find it less dangerous at first. However, delaying treating the white spark plugs may cause impending performance and engine damage. I suggest you read this entire blog post and find out why you are getting to see white spark plugs.

Normal vs. Abnormal Spark Plug Colors

The fact is that spark plug color is a tell-tale sign of your engine’s condition. As I said, a healthy component has a light brown or grayish-tan appearance or an insulator-firing nose. It ensures that the spark plug operates at optimal temperature and the engine is in good condition.

Now, the abnormal scenarios with spark plugs can be like these:

Dark Deposits

Oil leakage, fuel quality, and the engine’s operating duration influence the accumulation of deposits on the firing end. Thus, dark, black, wet, or dry deposits on the nose of spark plugs refer to these overly rich conditions:

  • Too cold a spark plug heat range
  • A possible vacuum leak
  • Low compression
  • Overly retarded timing
  • Too large a plug gap.

Wet deposits may hint at a breached head gasket or poor oil control from ring or valvetrain problems.


The accumulated deposits on the insulator tip melt when your vehicle has an overheated spark plug. It will give the insulator tip a glazed or glossy appearance. I will explain the reasons for overheating in the latter part.

Lead Fouling

Yellowish-brown deposits usually indicate lead fouling. You may not detect this condition using a resistance tester at room temperature (5). Mainly, it affects the engines using leaded gasoline.


Breakage of spark plugs usually happens due to thermal expansion and shock for sudden heating or cooling. This condition may result in poor starting and misfiring.

Why are My Spark Plugs White – The Reasons & Possible Solutions

Without spending your precious time, let me discuss the reasons. In this part, I will explain why the spark plug color changes. You will also learn how to deal with this matter – following easy steps!

Lean Air-Fuel Mixture

Lean air-fuel mixture means too much air and insufficient fuel in the combustion chamber. This condition can cause a whitish texture on the tip of the spark plug, which will be extremely dry (6).

Some causes of lean air-fuel mixture are:

  • Vacuum leaks: Cracked hoses, loose connections, or faulty gaskets cause unmetered air to enter the engine.
  • Faulty fuel injectors: Clogged or malfunctioning fuel injectors cannot deliver the correct quantity of fuel.
  • Incorrect air-fuel ratio sensor: Inaccurate readings from the sensor can make the engine adjust to an improper lean mixture.

If there is a lean mixture, your engine will hesitate upon acceleration. It may even stall during regular operation. Besides, it may consume more fuel to compensate for the lean condition (2). Sometimes, it may lead to higher levels of nitrogen oxides and other pollutants in the exhaust.


In short, you need to adjust the mixture to solve the condition. To do so, fix any leaks in the vacuum, replace faulty fuel injectors, and adjust the fuel pressure to the correct level.


An overheating engine can cause spark plugs to become white.

 Some reasons for engine overheating are:

  • Coolant leak or low coolant level: Insufficient cooling for a leak or low coolant can increase engine temperature excessively (1).
  • Faulty thermostat: A failing thermostat can prevent coolant from circulating properly. As a result, it will cause the engine to overheat.
  • Malfunctioning cooling fan: When the fan does not work correctly, it will not dissipate heat effectively.

If your engine is overheated, you will see a temperature warning light on the vehicle’s dashboard. Additionally, your vehicle will not perform well due to a loss of power and engine efficiency. In some cases, you will see steam or smoke from the engine.

Solutions to Overheating

If you find that spark plugs are becoming white due to overheating, do not get worried about it. I have suggestions for it, too. First, fix the coolant leak by replacing the leaky radiator or hose. You may also replace the stuck thermostat to keep the engine cool. Fix or replace the malfunctioning cooling fan to maintain optimal engine temperature.

Incorrect Spark Plugs Heat Range

Incorrect spark plugs can cause white powdery deposition on the tip of them. Using a spark plug outside the manufacturer’s recommended heat range will overheat the plug and turn it white. It may also lead to losses in power, speed, and fuel efficiency (7).

Let me explain this matter in more detail.

The heat range of a spark plug indicates the rate at which the spark plug dissipates its firing end heat to the engine. However, an incorrect range can significantly affect engine performance. Too cold heat range can cause the spark plug to fail to self-clean by burning off carbon deposits. Conversely, if the heat range is too hot, the engine could experience detonation, pre-ignition, or power loss (8).


You should always use the recommended spark plugs for your vehicle engine. You can check out the expert’s opinion regarding this selection.

Incorrect Spark Plug Gap

You may not think about it, yet an incorrect spark plug gap can also cause plugs to turn white. Suppose the gap between the spark plug electrodes is not set to the vehicle manufacturer’s specifications. Then, it can affect combustion efficiency and increase engine temperature. Damage or wear on the plug can cause improper sparking and overheating .


You should ensure the gap between the spark plug electrodes is set accordingly. If you cannot do it or the electrodes are not in good condition, I suggest you replace the spark plug.

Carbon Buildup

Sometimes, carbon buildup may turn your spark plugs into white.

Some causes of carbon buildup are:

  • Incomplete combustion: Poor combustion leaves carbon deposits on the spark plugs.
  • Using low-quality fuel: Fuel with high levels of impurities can contribute to carbon buildup. Also, it may not burn efficiently.
  • Engine wear and tear: Worn components cause inefficiencies and increased carbon deposits, which you may get in white on the electrode tip.

When your engine misfires, get less power from the engine, and idle roughly or unevenly, consider that there is a carbon buildup on the spark plugs.


Ensure the air-fuel mixture and ignition timing are correct to maintain better combustion efficiency. Also, avoid using low-quality or non-recommended oil for the engine. Replace any damaged components to get the engine performance back to normal.

How to Clean White Deposits from Spark Plugs

You can follow different methods to clean white deposits from the spark plugs (9,10). Please check out the below table:

Using a wire brushRemove the spark plugs. Disconnect the negative terminal of your vehicle’s battery. Use a wire brush to scrape off the white deposits. Apply a little gasoline or WD-40 for stubborn deposits
Using an ultrasonic cleanerFill the ultrasonic cleaner with water and a cleaning concentrate.Dip the spark plug into the mixture.Leave it for 15-25 minutes at about 50°C.Dry it.
Using soda and saltPlace the plug in a container.Pour soda until it completely covers the plug.Add some salt.Wait till the soda and salt bath works fine.Brush off the loosened deposits using a wire brush.
Using a blow torchUse pliers to hold the spark plug.Apply the blow torch to it for 1-2 minutes.Avoid cooling the spark plugs with water after torching.. Allow them to cool on a dry surface.
Using chemical cleanersDegrease the spark plugs with a solvent.Submerge the electrode end in a cleaning agent. Leave them for several hours while monitoring the deposit removal rate.Rinse the spark plugs again with solvent.Dry them.
Using sandpaperFold the sandpaper in half.Clean the plaque in the gap between the electrodes.

Final Words

I hope you know the answer: “why are my spark plugs white?” I have covered everything related to this issue. So, there is only a little left to do if you find white spark plugs in your vehicle engine.

Inspect the plugs to learn what’s causing them to become white powdery. Again, follow the solutions I have suggested.

Thank you for reading this blog post. Good to see you here!

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