Why Is There Oil In My Air Filter? (All You Need To Know!)

Air filter with oil coating

Many air filters have an oil layer on their filtering material.

This can be confusing since you can mistake it for some engine oil spillage onto the filter easily.

So, why is there oil in the air filter? Most air filters, especially cotton gauze and foam air filters, are coated with oil. The oil in these filters will prevent any dirt or dust particles in the air from passing through. These contaminants get stuck in the oil layer of the filter.

Let’s deep dive into why oil on your air filter is not a big concern and what to do if there is actually engine oil dripping from the air filter.

Why is there oil on the air filter?

The oil on an air filter exists by design to filter contaminants more efficiently.

Most air filters, specifically cotton gauze filters and foam filters are coated with an oil layer over their filtering material.

This oil layer over either the cotton gauze or the foam helps in preventing air dust and dirt particles to enter into the filter.

What in turn happens is there contaminant particles get stuck with the air on the filter surface, thereby letting only the clean air to enter.

Put simply, the oil layer applied on the air filtering material helps to filter air contaminants more efficiently.

Is it normal for oil to be on an air filter?

As mentioned above, it is normal for the oil to be on an air filter.

There is no need to freak out.

Your air filter is just working fine.

In fact, an oil layer over the filtering material, especially if the material is cotton gauze or foam, helps in preventing the dirt and dust particles to enter into the engine.

So, the oil layer is totally fine, and no need to worry about it.

Another advantage of an oil layer is it protects the filtering material and improves its life span. the filter material will last longer this way.

All you need to do is clean the filter and re-oil it up and the filter is good to go again. You don’t need to replace them every time the filter gets clogged up.

What if it is motor oil on the air filter

Now, this is a concern.

If there is motor or engine oil on your air filter, here is what you need to do:

First, double check it is motor oil on the air filter.

The engine or the motor oil has different colors – either orange or reddish-brown. And even black if you haven’t changed the oil for quite some time.

The oil on the air filter, on the other hand, is mostly transparent in color. So, make sure the oil you are seeing on your air filter is indeed the motor oil.

Second, check the engine oil levels. Most likely what would have happened is you might have overfilled the engine oil and hence there is oil spillage from the engine crank case.

If this is the issue, drain out some engine oil to optimum levels.

However, if this is not the case, check the engine crank case for any signs of oil spillage. This is not a norm, but if this happens to be it, you need to address the oil spillage issue. Better to take your motorcycle to a service shop or a dealer.

Lastly, take out your air filter and clean it up.

If there is too much of motor oil spilled on the air filter, you might have to replace the air filter entirely.

How do you get oil out of your air filter?

If it is not the motor oil on the air filter, there is no reason to get rid of the oil.

However, if it is indeed motor or engine oil spilled on the air filter, it is better to consider replacing the air filter entirely first.

Air filters do not cost much and having motor oil on the filter is a messy thing to clean up.

However, if you still wish to clean the oil away from the filtering material, you can go ahead. Remove the air filter from the motorcycle first.

Take out the filtering material and rinse it in a soapy water solution. Alternatively, you can use a branded cleaner kit for a thorough cleaning.

Once you have cleaned the filter from all the dust and the oil, you need to dry it out. Use compressed air to dry clean the filter completely.

Once cleaned and dried up, you can fit the air filter back into your motorcycle.

Can a dirty air filter cause an oil leak?

While it is not usual, a really dirty and clogged air filter can cause the engine oil to leak.

A highly clogged air filter will restrict air entry into the engine. As a result, there is a vacuum created in the air flow path that flows from the filter all through to the engine.

Couple this with worn out piston rings or oil seals, the oil gets pulled by the vacuum in the air flow passage.

This can cause the oil to flow from the crankcase all through to the air filter.

As a consequence, you might see engine oil dripping from the filter at times when the filter is too dirty and clogged up.

Time to clean or replace that air filter then.

What if oil is dripping from the air filter?

If there is oil dripping from the air filter, then it is most likely the engine oil and not the oil layer applied on the filter by design.

First thing, take out the air filter and clean it using soap water solution or a cleaning kit. An air filter covered with engine oil will not function smoothly and will restrict the air flow into the engine further.

Next, check the root cause for why there is engine oil dripping from the air filter.

Usually, it can be because the piston rings are worn out, oil seals are damaged, or the oil passages are clogged up.

Check and address the cause for the oil spillage because even after the air filter cleaning, you will gain see the oil dripping if you haven’t addressed the main issue.