Why is There Oil in My Air Filter? Unraveling the Mystery!

why is there oil in my air filter

Any person who works with equipment with an engine like a vehicle, a generator, a water Pump, and any other machinery will sometimes come across the question, “Why is there oil in my air filter?” There will be very simple reasons, such as the air filter comes with oil applied on the surface to replace the engine. This article will explain the reasons for this issue and why an air filter is required. It will also give an insight into how an engine works and what should be done to prevent oil in the air filter.

What is the Purpose of an Air Filter in a Vehicle’s Engine?

Usually, engines run on fuel which means the engine burns the fuel to generate power to turn the wheels on. This is done by burning the fuel inside the cylinder, which causes the piston to move.

This movement is then used to move/turn other parts/wheels, and eventually, this power is transmitted to the tires, which makes a vehicle move.

To burn the fuel, air is necessary, as with no air, no burn will occur. So, why need an air filter? If the air is contaminated by solid particles, dust, or other contaminants that will block the air supply, the burn will not be efficient. And if the said particles make their way to the burning chamber, they could damage the piston, piston rings, valves and cylinder wall. Thus an air filter is required for smooth engine running.

Why Would Oil be Present in the Air Filter Housing?

Oil is used in an engine to reduce the friction among the moving parts. A very small quantity of oil will be inside the cylinder as the piston rings will not be fully sealed against the cylinder wall. When an engine runs, pressure will build up from the air, fuel, and oil slipping past the Piston rings, called a “blow-by”.

Excessive pressure will build up inside the cylinder when oil, fuel, and air are burnt. This mixture will burn more quickly, and the pressure will increase as the oil quantity increases.

A system called positive crankcase ventilation (PCV) is used to avoid the buildup of excessive pressure and moisture. This opens a valve and regulates the airflow.

This gives fresh air for burning but sucks blow-by gasses down the PCV valve. When the PCV valve gets clogged, the engine blow-by (with oil) is pushed to the air filter through the air intake.

What are the Symptoms of Oil in the Air Filter

What are the Symptoms of Oil in the Air Filter?

As explained earlier, oil can be seen in the air filter or housing when the positive crankcase ventilation valve is clogged. There are many reasons why it can get clogged. Though there could be a small blow-by as a small amount of oil can slip into the combustion chamber through the piston rings, an excessive oil blow-by will burn more oil which can be noticed when an oil change is done.

Burning of oil will generate white smoke emanating from the exhaust pipe when the engine is running. The engine’s fuel efficiency and horsepower will decrease when the blow-by gets condense and settles between the head and the cylinder masking the air and gas intake.

Engine oil mixed in the air & fuel will result in an incorrect mixture which will make the engine cause pre-detonation causing an engine knock.

Condensed and settled blow-by can cause the spark plugs to misfire and possibly the accumulation of flue in the combustion chamber.

Can Oil in the Air Filter Indicate a Problem with the Engine?

Though oil in the air filter does not indicate engine frailer, it should not be ignored. There are some aftermarket air filters where oil should be applied on the external surface to capture dust and other particles.

If an excess amount of oil is found in the interior of the air filter, it should be due to a clogged positive crankcase ventilation valve as the oil is leaked to the combustion chamber through the piston rings.

As a result, more carbon will form on the piston ring grooves resulting in more oil leaking through the rings.

More oil burning will produce more residues and more carbon. However, a little blow-by is a natural thing. If ignored, eventually, it will cause severe damage to the engine.

How to Fix the Oil in the Air Filter?

There are several reasons for oil to be in the air filter or the air filter housing, and there are several ways to handle the situation.

  1. Replacing the Positive Crankcase Ventilation Valve

PCV Valve is used to redirect blow-by back into the air intake. It works as a filter and captures the oil in the blowback. The PCV valve should be replaced as recommended by the manufacturer. The oil will reach the air intake system through the valve if not replaced.

  1. Using Original Air Filters/Aftermarket Air Filters

Some aftermarket filters are oiled from the outside to capture the small particles. Does not do any harm.

  1. Changing Engine Oil in Time – to Avoid Clogged Oil Passages

This happens when the oil is not changed in due time. The oil will create engine sludge and excessive carbon deposits, resulting in oil pressure inside the engine. This will force the oil through the PCV valve to the air intake.

  1. Replacing Worn Piston Rings/Piston

piston rings are used to seal off the combustion chamber to avoid gas leakages and to avoid engine oil flow. When the piston rings are damaged, the engine oil will flow into the combustion chamber and go to the air filter, as explained. Similar results could be seen with worn-out pistons.

Are there Specific Engine Issues that Can Lead to Oil in the Air Filter?

The following engine issues can lead engine oil to the air filter.

  • The PCV valve should be replaced as recommended by the manufacturer. The oil will reach the air intake system through the valve if not replaced.
  • Overused oil will create engine sludge and excessive carbon deposits, resulting in oil pressure inside the engine. This will force the oil through the PVC valve to the air intake.
  • Damaged/ Worn-out Piston rings and Pistons will allow engine oil to be flown into the combustion chamber, which eventually ends up in the air filter.

Thus, these reasons may cause severe complications in your air filter, leading to a colossal bill at your hand as you will have to consult a technician if not treated earlier in the problematic stages.

Watch this one,

Video Credits – Automobile basic ideas

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