EXPERT IN AUTO PARTS
20 March 2025 (updated) Table of content
Oil on spark plugs is a warning sign that should never be ignored, as it can indicate underlying engine issues that may lead to reduced performance or costly repairs. Whether caused by worn piston rings, faulty valve seals, or other mechanical problems, this issue can result in misfiring, increased fuel consumption, and excessive emissions. Understanding the causes, symptoms, and potential consequences will help you address the problem early and keep your engine running smoothly.
The most common symptoms of oil on spark plugs include:
Ignoring these symptoms can lead to severe engine damage, so it is crucial to diagnose and resolve the problem promptly.
Read Now
Recommended Article
How to test a spark plug
Oil on your spark plugs can result from worn piston rings, damaged valve seals, excessive crankcase pressure, or a failing PCV valve.
-24%
Article number: 1496
compared to
RRP
£ 23,65
£ 17,93
Price per item
price incl. 20% VAT, excl. delivery costs
-58%
Article number: Z332
compared to
RRP
£ 24,01
£ 9,94
Price per item
price incl. 20% VAT, excl. delivery costs
Article number: 90911
£ 14,49
Price per item
price incl. 20% VAT, excl. delivery costs
-19%
Article number: 97098
compared to
RRP
£ 15,54
£ 12,53
Price per item
price incl. 20% VAT, excl. delivery costs
-25%
NGK Spark plug
M14 x 1,25, Spanner Size: 16 mm
Article number: 91898
compared to
RRP
£ 19,16
£ 14,27
Price per item
price incl. 20% VAT, excl. delivery costs
A blown head gasket can cause oil on spark plugs by allowing oil to leak into the combustion chamber. When the gasket fails, it can no longer seal the oil, coolant, and combustion gases properly, leading to contamination. This can result in poor engine performance, misfires, and excessive smoke. If left unaddressed, it may cause severe engine damage, requiring costly repairs or even a complete engine rebuild.
If your spark plugs are loose, they can contribute to oil buildup on them by failing to maintain a proper seal. A loose spark plug may not create a tight connection with the cylinder head, allowing oil from leaking valve cover gaskets or worn O-ring seals to seep into the spark plug well. Over time, this can lead to engine misfires, reduced performance, and potential damage to the ignition system if the issue is not resolved. Ensuring that spark plugs are properly tightened and inspecting the surrounding seals can help prevent oil contamination and maintain optimal engine function.
A bad PCV (Positive Crankcase Ventilation) valve can cause oil on spark plugs by disrupting the engine’s ventilation system. A faulty PCV valve may fail to regulate crankcase pressure, leading to excessive oil buildup and forcing oil into the combustion chamber. This can result in oil fouling the spark plugs, leading to poor combustion, misfires, and reduced engine efficiency. Replacing a malfunctioning PCV valve is a simple yet crucial step to prevent oil contamination and ensure the engine operates smoothly without excessive oil deposits on the spark plugs.
Oil on spark plugs can lead to serious engine issues, affecting performance and longevity. When oil seeps into the combustion chamber, it disrupts the spark plug’s ability to ignite the air-fuel mixture properly, resulting in inefficient combustion and various problems.
One major consequence is engine misfires, where incomplete combustion causes rough idling, hesitation, or even stalling. This can lead to further damage if left unaddressed. Reduced fuel efficiency is another issue, as oil-coated spark plugs fail to generate a strong spark, forcing the engine to burn more fuel to compensate.
Over time, carbon buildup may occur on the spark plugs and within the combustion chamber, increasing the risk of engine knocking and premature wear. Additionally, excessive oil consumption can indicate an underlying issue, such as worn piston rings or valve seals, which, if not repaired, may lead to engine overheating and potential failure.
If oil on the spark plugs is ignored, the catalytic converter could also suffer damage due to unburnt fuel entering the exhaust system. This not only affects emissions but can also lead to costly repairs.
To avoid these complications, it is crucial to diagnose and resolve the root cause of oil contamination. Regular maintenance, including timely spark plug replacements and checking for leaks, ensures optimal engine performance and prevents costly damage.
Yes, oil on spark plugs can cause engine misfires. When oil contaminates the spark plug, it interferes with the spark’s ability to ignite the air-fuel mixture effectively. This leads to incomplete combustion, causing misfires, rough idling, hesitation, or stalling. If left unaddressed, misfires can damage the engine over time, reducing performance and potentially leading to more severe mechanical problems.
-51%
Article number: Z90
compared to
RRP
£ 12,91
£ 6,28
Price per item
price incl. 20% VAT, excl. delivery costs
-48%
DENSO Spark plug
Spanner Size: 16
Article number: VXUH20I
compared to
RRP
£ 31,83
£ 16,34
Price per item
price incl. 20% VAT, excl. delivery costs
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 14
Article number: 0 242 129 510
£ 5,41
Price per item
price incl. 20% VAT, excl. delivery costs
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 14
Article number: 0 242 140 565
£ 16,34
Price per item
price incl. 20% VAT, excl. delivery costs
-32%
NGK Spark plug
M14 x 1,25, Spanner Size: 16 mm
Article number: 94167
compared to
RRP
£ 33,67
£ 22,75
Price per item
price incl. 20% VAT, excl. delivery costs
Yes, oil on spark plugs can cause a rough idle. When oil leaks onto the spark plugs, it disrupts the ignition process. As a result, the spark plugs struggle to generate a strong, consistent spark, leading to incomplete combustion. This causes the engine to run unevenly, resulting in a rough idle. The engine may shake or vibrate at low speeds, especially when stopped at traffic lights or when the engine is in neutral. If left untreated, it can lead to further engine performance issues.
To stop oil from getting on spark plugs, it is essential to identify and fix the root cause. Common solutions include:
Addressing these issues will help keep oil from reaching your spark plugs, ensuring better engine performance.
Read Now
Recommended Article
TOP 5 best spark plugs
To fix oil on spark plugs, first remove the spark plugs and inspect for oil contamination.
Next, check for any signs of a faulty valve cover gasket or worn piston rings. If the gasket is damaged, replace it to prevent oil leakage onto the spark plugs. Clean the spark plug holes and install new spark plugs for your car if necessary.
You should also inspect the ignition system for any other issues, such as worn-out coils, which could affect performance. Once everything is cleaned and replaced, reassemble the components, ensuring the valve cover is sealed correctly. Reinstall the spark plugs and test the engine for smooth operation. If the problem persists, further investigation into the engine's internal parts may be needed.
Top products related to this topic:
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 14
NGK Spark plug
M14 x 1,25, Spanner Size: 20,8 mm
NGK Spark plug
M12 x 1,25, Spanner Size: 14 mm
NGK Spark plug
M14 x 1,25, Spanner Size: 16 mm
BOSCH Spark plug
M 14 x 1,25, Spanner Size: 16
NGK Spark plug
CNG/LPGM14 x 1,25, Spanner Size: 16 mm
BOSCH Spark plug
M 12 x 1,25, Spanner Size: 16
BOSCH Spark plug
M 14 x 1,25, Spanner Size: 16
NGK Spark plug
M12 x 1,25, Spanner Size: 14 mm
NGK Spark plug
M12 x 1,25, Spanner Size: 16 mm