Updated at: 15-07-2022 - By: Lucas

The source of ignition is the spark plug, a minor but critical part of the engine’s internal combustion. Initiates the fuel/air mixture in the engine’s combustion chamber with an electrical spark. To put it another way, the car’s spark plug ignites the engine by moving the pistons.

The compressed air and fuel in the combustion chamber are continually burned by the spark plug to power and maintain the car’s engine.

Furthermore, these components can burn off fuel additives and any impurities deposits, so it can resist extremely high temperatures.

Despite the fact that the spark plug is an essential part of your car’s operation because it is necessary for it to start and move, problems can arise with it.

It’s easy to spot a faulty spark plug since your engine’s performance may suffer, it may misfire while accelerating, and it may even have issues starting cold. Furthermore, a spark plug with problems will have an impact on the vehicle’s fuel economy, resulting in higher gasoline consumption.

Oil fouling, which occurs when oil enters the combustion chamber, is a typical problem that affects spark plugs. There is an effect on ignition when the spark plugs are clogged with oil. Spark plug arcing is prevented by the oil elements depositing on the plug’s surface and forming a cover.

Head gasket leaks, a defective seal valve guide, a rich fuel mixture, and worn piston rings or cylinders are all typical reasons of spark plug fouling.

The spark plug is pushed to follow a short path through the oil when it comes into contact with the ground. But why do oil-covered spark plugs fail to ignite?

The following are common reasons of oily spark plugs:

1. Damage/worn cylinders or piston rings

It is possible for oil to enter the combustion chamber and foul the spark plugs if the cylinders or piston rings are cracked or worn.

2. Bad or worn valve guide seals

A tight seal is impossible without the assistance of valve guides. Oil can enter the combustion chamber through the valve stem if the valve guide has a problem. Black, moist oil impurities occur in the combustion chamber and are deposited on the spark plugs as soon as oil reaches the chamber.

3. Leaks from a damaged head gasket

In your car, the head gasket plays a crucial role in keeping coolants out of the combustion chamber by acting as a seal.

Coolant can leak into the ignition chamber if the head gasket has lost its seal power, causing moist, oily deposits on the spark plug. A leak in the head gasket is bad news because it will cost a lot to fix or replace the head gasket.

4. A rich fuel mixture

An overly rich fuel mixture may be at blame if significant dry carbon deposits are seen on the spark plugs. Fuel pressure regulator deactivation or a clogged fuel return line may have contributed to a rich fuel mixture. Having a problem with the fuel pressure regulator will cause the mixture to be too rich.

5. Clogged oil system ventilation

When a problem with the oil system is to blame, the spark plugs become clogged with oil. In this case, there are only two options available.

Solutions for oil-fouled spark plugs?

Oil Fouled Spark Plug-1

Of course, you’re not going to be able to drive about in a car that awful. If your car’s spark plug is clogged, it won’t start and won’t drive anywhere.

To fix a spark plug problem, you must first determine the source and cause of the problem. The following are some potential remedies for spark plug fouling, which is a regular occurrence.

1. Replace or repair flawed, damaged, or worn cylinder walls and piston rings.

It’s possible to do this if piston rings or cylinders are to blame for oil getting into the combustion chamber.

3. Replace valve guides

A replacement valve guide should be installed if oil leaks into the combustion chamber due to a defective valve guide. Valve guides are designed to keep oil from leaking into the engine’s internal combustion chamber.

4. Repair or replace the bad or leaky head gasket

Even though fixing a faulty head gasket is expensive, doing so is necessary because it prevents coolant from entering the combustion chamber when the engine is running.

If your cooling system’s head gasket sealer or cooling unit sealer bottle has to be repaired, this is a low-cost solution.

5. Check the oxugen sensor, plugged fuel return line and the fuel pressure regulator

Indicators of a rich fuel mixture include a heavily carbonized spark plug. When there is a high ratio of oxygen to fuel, the fuel mixture becomes rich.

Fuel return line and pressure regulator malfunctions are the most common causes of oxygen sensor failure in these scenarios. The spark plug will foul if the jetting is improper, the fuel inlet needle valve is leaking, or the float is set incorrectly.

Should spark plugs be covered in oil?

In order for the engine to function properly, oil is a vital lubricant. Overheating will occur if the moving parts rub against each other because of a lack of lubricant.

Oil should not be applied to spark plugs, though. If you detect oil on your spark plugs, you should have your car inspected right away.

Valves cover gaskets can fail, as might a head gasket, piston ring, valve guide, or spark plug gasket. In addition, if the spark plug has oil in it, it could signify that gasoline and oil have been mixed.

What happens if oil gets on spark plugs?

Oil Fouled Spark Plug-3

Engine performance and oil usage are affected when oil seeps into the spark plugs, resulting in blue smoke from the exhaust and misfires.

An engine fire might occur if oil makes its way to the spark plugs. So, if your vehicle exhibits any of these signs, have it inspected as soon as possible.

Can oil on spark plugs cause no start?

Cars that won’t start due to grease on the spark plugs are real. This means that the oil may have shorted out every one of the plug wires and coils, causing the engine to not start.

The valve cover gasket must be replaced if oil is pouring into the galley from a leaking valve cover. After emptying the oil from the galley, be sure to change the spark plugs as well.

Can bad spark plugs cause oil burning?

The two are not connected in any way. The engine runs rough because of poor oil combustion as a result of faulty spark plugs. The check engine light will come on as a result of oil getting on the spark plugs.

Catalytic converters might malfunction or overheat if there is too much oil in the exhaust. Components that wear down over time are the most likely to cause oil burning in a vehicle.


The health of an engine can be indicated by faulty spark plugs. Spark plug fouling is a sign that the engine’s combustion chamber is having issues, such as oil seeping in.

To prevent more damage and more expensive repairs, you must have the problem diagnosed and fixed as soon as possible for the sake of your car’s safety and performance.