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Oil In The Air Filter – Here’s What You Need To Know

Changing The Cabin Air Filter

When figuring out the detriments of having oil in the air filter in your vehicle, you need to be aware of the importance of engine oil, the function of the air filter, and signs and symptoms of a damaged air filter. Since oil in the air filter can lead to engine issues, transmission problems, and concerns about the air circulation within the vehicle, keeping oil out of the air filter and the air filter free of debris should be a top priority for all drivers. 

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What is engine oil?


Before we can look at the air filter’s function in your vehicle and how oil in the air filter can harm your car’s components, we need to know what engine oil is. Oil is the primary function and lubricant housed within the engine, used for various functions that involve allowing the engine to run at a high-performance level. 


  • Function of Engine Oil



The essential purpose of this in your engine is to reduce friction, promote cooling and prevent overheating, encourage sealing of connections, clean to remove built-up debris and contaminants, and serves as protection for the moving parts that can create excess stress inside of the engine. If you notice oil in the air filter, you might notice the lack of benefits typically provided by this lubricant. 


However, despite all of these critical engine oil functions, it is often overlooked and does not get the credit it deserves. 


  • Engine Oil Mechanisms



Engine oil does its job of providing a fluid barrier between overheating moving parts to prevent excess friction and wear and tear. Along with the prevention of overheating, the engine oil provides almost half of the engine’s cooling properties, allowing the coolant or refrigerant to travel around the engine and cool off the heated parts. 


The engine oil forms a seal between various parts inside of the engine, like the piston and the cylinder walls, reducing wear, providing the right compression, and keeping the proper air and fuel ratio. However, if the oil remains stuck inside the air filter, the oil might not be doing the correct job. 


In order to keep engine oil working at the right temperature, performance level, and not getting oil in the air filter, you need to perform regular maintenance and oil changes to keep the levels high enough and the engine at the right thickness or viscosity. This can be done by performing regular oil changes at specific intervals to prevent oil in the air filter. 

What is the air filter?


Now that we know what oil is and the important oil function in your car, we need to know what an air filter is. Just like any other filter, the air filter in your car helps the engine “breathe” easier, allowing it to work more efficiently with the same amount of fuel or air. Make sure you keep an eye on the air filter and your engine by taking note of your car’s grill – if you see all the grime splattered on the front of the car, this grime can also make its way to the engine, harming the performance. 


The air filter in your car mainly functions to provide this built-up debris and contaminants from harming the engine. Usually, the air filter will be placed in the plastic box to prevent the contaminants from escaping. However, sometimes you might find the air filter’s oil is harming the engine’s cooling and performance capabilities. 


In theory, your car’s air filter could get so dirty over time and build up so much debris that the engine would not run at all. However, we hope you keep an eye on your car and engine performance before getting to this point. If you notice that there is oil in the air filter, you need to come up with a quick solution.


What is more likely in most cars is that the dirty air filter will not allow the engine to get the proper amount of fuel or air to work correctly, harming the performance levels and causing oil to be trapped in the air filter. New, fuel-injected systems in modern cars have proven that a healthy and clean air filter can keep the engine working at the right horsepower. However, if you have oil in the air filter, the power produced from the engine will be much lower. 


Your typical oil filter and the air filter have a vital job for being such a small vehicle component. The oil filter is in charge of cleaning your car, preventing any dirt and debris from getting to the car’s heart – the engine. Over time, if you let the oil filter get clogged, like having oil in the air filter, the filter will no longer clean the fuel or oil, causing your engine to produce harmful contaminants. 


Although the air filter might seem like a minor part compared to more extensive mechanisms in your vehicle, like the engine or the transmission, oil in the air filter can be very detrimental. This problem can further lead to issues with the engine and transmission in your vehicle, causing an expensive replacement. 

Types of Car Air Filters

As we know by now, car air filters are key to purifying the inside air of your car, allowing you and your passengers to have clean, uncontaminated air. What you may not know is that car air filters come in two main types.


  • Panel Style


The panel style is used in most cars on the market today. The panel style is used in fuel-injected cars, which are modern vehicles that do not require a carburetor to supply the engine with enough gas properly. 


  • Radial Style


The air filter’s radial style is used in carbureted vehicles and has a chance of oil getting in the air filter. This car air filter is usually housed in a black plastic casing near the engine’s top. 

Causes of oil in the air filter

Oil in the air filter can result in blow-by when the combination of the air and fuel located in the engine or the combustion location escapes. The air and fuel mixture makes its way into the crankcase, causing the engine under-performance. 


  • Engine blow-by


Luckily, some key signs of engine blow-by can alert you to oil being in the air filter. Among these noticeable symptoms to drivers and passengers are engine misfiring, clouds coming from the exhaust, a white exhaust coming out of the car, the coolant in the engine oil, and the engine knocking.


So, why should you care about engine blow-by? This phenomenon can greatly reduce fuel efficiency and the performance of the engine. Since the air and fuel are pushed into the crankcase, this lowers the fuel economy and the horsepower, causing the air and fuel to be wasted. 

What causes engine blow-by

Many parts cause the engine blow-by in your vehicle. As you know, to determine why there is oil in the air filter, you need to see the main mechanism in your car or the part that is causing the piston rings to not properly seal, leading to a lower engine life and performance capabilities.

The engine blow-by’s most common causes are typically traced back to three parts – the pistons, piston rings, and cylinder walls. Usually, you will find engine blow-by the symptom of damaged piston rings, which leads to a lack of tight connections and tight seals. 


  • Faulty PCV valve


If you have a clogged or debris-filled positive crank ventilation valve, this can be a common cause of oil in the air filter. The PCV has the main function of recirculating the wasted gases back to the air intake valve, traveling then to the combustion chamber to have an opportunity to re-ignite to be used properly. 

When the PCV valve shuts, it can get clogged due to a build-up of debris and dirt. If this occurs, the engine’s blow-by gases have to be forced through other gaps instead of the valve. This causes leaks and improper fuel and air mixture, leading to oil in the air filter. 


  • Worn Piston Rings


The second cause of engine blow-by and oil in the air filter is damaged piston rings. The piston ring is positioned between the cylinder wall and the piston, in charge of keeping a tight seal of the gases within the combustion chamber and the engine. A faulty seal and a loose connection mean that gas can escape the combustion chamber and cause the oil stuck in the air filter.

The piston rings can easily succumb to wear and tear due to the location of the parts. If your engine has extensive wear and high stress, this can lead to a broken or damaged piston ring. To figure out if you have a faulty piston ring, you need to check the cylinder’s pressure, ensuring the number is the same within all cylinders. 


  • Clogged Oil Path


Although oil and oil filters can be used for thousands of miles and have relatively long lifespans, oil can still get stuck in your air filter, leading to a clogged and debris-filled oil transportation path. It is important to keep in mind that oil will not last forever, so you still have to perform regular maintenance and perform regular changes. 

In addition to the oil in charge of lubricating the system and flushing out the toxins, the oil can create sludge build-up and lead to clogged pathways and seals. This sludge can accumulate in places like the air intake, leading to reduced engine power, lower lubrication levels, and oil in your air filter. 


  • Aftermarket Air Filters


Air filters are in charge of keeping out debris, toxins, contaminants, and dirt that can slow down lubrication travel and harm the engine’s performance. Since the air filter works in such a high-traffic area, an air filter can have extensive wear and tear after prolonged use. 

Some air filters might be reusable – but some won’t. If you continue to use air filters that are not meant to be reused, then you will notice oil in the air filter. If you notice that there is oil located inside of the filter, too much oil could be the problem. 

When To Replace an Engine Air Filter

When looking at how to prevent oil in the air filter, you need to replace your air filter at specific intervals to keep it working properly and efficiently. The best thing you can do for your air filter? Replace the air filter at the indicated intervals in your car’s owner manual before noticing any symptoms of a damaged filter. 

Most car owners should replace their air filters at around 30k miles. If you want to be on the safe side to prevent any further damage, you should look to replace the air filter between 15k and 30k miles. 

If you want to get your mechanic’s advice, you should have your oil changed and checked during every normal routine maintenance procedure. Sometimes, mechanics will be able just to clean the air filter and avoid a replacement charge. 


As you can see, the air filter is a key part of your car’s performance, health, and efficiency. By keeping oil out of the air filter, you can keep the car’s air clean and debris-free. Suppose you decide to wait between oil changes. In that case, you do not adhere to a maintenance schedule, and you forget to change the air filter, you could be looking at a contaminated engine supply that can harm your engine’s effectiveness. 

Keeping your air filter free of debris, dirt, sludge, and contaminants promotes a healthy care, healthy air quality, and healthy fluid transportation throughout your vehicle. With a working air filter that transfers clean air throughout the cabin, you can make sure that you and your passengers have a comfortable ride. 

In addition to the high air quality provided by the clean air filter, keeping oil out of the air filter ensures that the engine performance does not decline, the oil levels remain at the proper levels to lubricate engine parts, and the transportation of fuel and air throughout the vacuum and air lines works efficiently and quickly. 

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