Oil in the Air Filter – What You Should Know

The air filter helps prevent debris, particles, dust, or other contaminants from entering the air and fuel mixture during combustion. But is it normal to see oil in the air filter? The answer is a bit complicated. 

Oil shouldn’t get to your air filter, but it is not unusual to see it. Oil in the air filter may indicate more serious mechanical issues like clogged crankcase because of sludge growth inside, abnormal carbon deposits, and more.

Worst, if left unattended, it may result in engine “blow-by,” a condition where combustion gases leaks between the cylinder and piston to the crankcase. In this article, we have explored the reasons, results, and removals of air filter oil. Read on.

What are the Main reasons for Oil in the Air filter?

The presence of oil in the air filter may be caused by a clogged PCV (Positive crankcase ventilation) valve, excessive oil refill, damaged oil filter, worn out piston ring, aftermarket reusable filters, extreme engine pressure, and clogged oil passage.

Let’s examine some of the issues highlighted above:

Clogged Positive Crankcase Ventilation:

A clogged PCV valve may be responsible for oil in the air filter.  The PCV helped to control blow-by gasses into the intake rather than directly to the surrounding.

When the PCV valve is clogged, these gases don’t escape normally; pressure is built within the crankcase.  Subsequently, this increased pressure forces oil past the gasket and seals up to the air intake system.

Like the oil filter, the PCV valves should be replaced regularly, or it becomes clogged with combustion by-products like sludges, debris, and other contaminants. We recommend changing your PCV valve every 30,000 miles.

Worn-out piston

The piston is housed within the engine cylinder, maintaining a tight seal and keeping the oil intact. Its oil allows for proper piston lubrication, preventing the engine from knocking.

However, when the piston is weak, its seal also becomes weak, allowing for blow-by. In addition, oil escapes back into the combustion chamber, where it can get into the intake manifold. Usually, the PCV valves take care of these gases, but if the oil is much, that may fail too. In addition, the worn-out piston can get oil in the intake pipe turbo.

Clogged oil passage

Oil passages are channels in which oil circulates within the engine. These channels help the oil move contaminants that may have escaped into the engine. If these channels become clogged with these contaminants, it can cause serious problems.

Blocked channels disrupt the oil flow, increasing heat pressure within the engine.  The heated oil tries to find alternative routes and sometimes forces its way into the combustion chambers and crankcase.

Aftermarket reusable filters

Most aftermarket air filters are designed with oiled foams, which may contribute to the presence of oil in the filter.

The filter is often pre-oiled to enhance its ability to trap more dust and debris. If it is excessively oiled during maintenance or reuse, it may cause other mechanical problems.

For instance, the excessive oil may cause contamination in the Mass Air Flow (MAF) sensor, causing incorrect errors and performance issues.

What will happen if Oil is in the Air Filter?

As emphasized above, oil in the air filter is often a sign of other mechanical issues in the car and should not be left unaddressed. Here is what happens if oil gets into the air filter:

Contamination of sensors: Excessive oil can contaminate sensors in the vehicle, including the MAF sensor, causing incorrect readings.

Damage to the Catalytic converter: When oil escapes into the air filter, it can be absorbed back into the combustion chamber and burned. The result is a by-product gas much harder for the catalytic converter to process. This by-product can coat the internal surface of the converter, clogging it completely.

Potential damage to the Spark plug: Oil-soaked plugs can damage the plug, causing a series of engine misfires and rough idling.

Reduced engine performance: The air filter helps to maintain the correct air-fuel ratio during combustion. Once the air filter becomes damaged, these readings become incorrect, causing reduced engine performance.

How do you remove oil from an air filter?

To clean your air filter, ensure to unscrew the air filter from its housing. Proceed to clean the air filter with a suitable cleaner. We recommend using the recommended air filter cleaner and recharger to eliminate oil in the filters, like the K&N air filter cleaner pack.

Furthermore, cleaning oil from the air filter will depend on the air filter used in the car. Most air filters are designed to be used once and changed at intervals to maintain the car air-to-fuel ratio. Reusable air filters like the K &N air filters can be cleaned for reuse.

Before cleaning or changing your car’s air filter, address the primary issue causing oil to get to the air filters.  This includes:

Is it normal to have oil in the air intake?

No, finding excessive oil in air intake is not normal. It indicates potential damage to the engine. The air intake is designed to deliver clean and cool air to the engine combustion. Oil in the air intake contaminates the air, disrupting the combustion process. Furthermore, oil in the air intake can lead to other issues like reduced engine performance, damaged oil plug sensors, and other complications.

Note: This article is a great guide for most mechanical engines and will help you fix oil in the air filters of motorcycles, generators, and most mechanical products with pistons and engines.

Final Words

This article has examined oil’s meaning, causes, and implications in the air filter.  Also, answers to questions like “Why is there oil in my air intake hose?” and cleaning tips were discussed within the article. Changing your air filter regularly or cleaning it every 20,000-50,000 miles helps to improve the quality of air available during combustion. Never neglect oil in the air filter, which could indicate severe engine complications.