The method of cleaning the air filter depends on its type. Most cars use paper dry air filters, which are usually not recommended or suitable for cleaning with water or other liquids because water can damage the structure of the filter paper, causing it to lose its filtering ability and even allowing water to enter the engine.

However, there are also some oil bath air filters on the market (commonly found in older models or certain specific vehicles, as well as some high-performance air filters such as K&N), which can be reused and require regular cleaning and refilling.

Below are the methods for handling these two types of filters:

1、 Paper dry air filter:
The main treatment method for this type of filter is replacement, not cleaning. Because its filtering medium is specially treated paper, it will become ineffective after absorbing water.

If it is only a slight accumulation of dust, you can try the following methods (with limited effectiveness and not recommended as a routine method):
Remove the filter element: Open the air filter housing and remove the filter element.
Gently tap: In an open area, gently tap the edge of the filter element with your palm or a soft tool (such as a rubber hammer) to shake off any surface dust. Be careful not to apply too much force to avoid damaging the filter paper.
Blow with compressed air: Use compressed air (if available at home) to blow air from the inside to the outside of the filter element to remove dust. Do not blow air in reverse, otherwise it will press the dust deeper and block the filter pores. The distance should be moderate, not too close, to avoid damaging the filter paper.
Inspection: After cleaning, check again. If it is still very dirty or if the air intake is still not smooth after cleaning, the safest method is to directly replace the filter element with a new one.
Important Notice:
Never wash with water!
The cleaning effect is usually poor and may damage the filter element.
The most recommended and effective method is regular replacement, which is more reliable than trying to clean and can also ensure the cleanliness of the engine intake.


2、 Oil bath air filter (reusable type):
This type of filter consists of a metal casing and a filter element filled with specialized filter oil, designed to be washable and reusable.

Cleaning steps:
Remove the filter element: Open the casing and carefully remove the oil immersed filter element.
Clean surface dust: Use a soft bristled brush or hair dryer (cold air mode) to remove large particles of dust and impurities from the surface of the filter element.
Immersion cleaning: Soak the filter element in a specialized filter element cleaning agent (note: not ordinary oil stain cleaning agent or water!), and soak for the time specified in the cleaning agent instructions. If there is no specialized cleaning agent, sometimes mild soapy water can also be used, but its effectiveness and safety are not as good as specialized cleaning agents.
Brushing: Remove the filter element and gently brush the inner and outer surfaces of the filter element with a soft bristled brush (such as an old toothbrush or specialized brush) to remove any attached oil stains and carbon deposits. Pay attention to brushing the wrinkled parts.
Thoroughly rinse: Rinse the filter element thoroughly with clean warm water or a specialized cleaning agent diluent to ensure that all cleaning agents and dirt are washed away. Compressed air can be used to assist in drying the interior.
Completely dry: Place the cleaned filter element in a ventilated and cool place to dry thoroughly. Never expose it to sunlight or use hot air to force it dry, otherwise it may cause deformation or damage to the filter element. Ensure that both the inside and outside of the filter element are completely dry (usually taking several hours or even a day).
Refill the filter oil: After the filter element is completely dry, it is necessary to refill the dedicated filter element for oil filtration. Usually, filter manufacturers will provide matching filter oil. According to the instructions in the instructions, use a brush or spray to evenly smear or spray the filter oil on all surfaces of the filter element, especially the folded parts. Be careful not to overdo it, otherwise excess oil will enter the engine, which may cause problems such as oil burning and increased fuel consumption.
Static oil absorption: Let the filter element sit for a period of time (such as 15-30 minutes) to allow the filter material to fully absorb the filter oil.
Wipe off excess filter oil: Gently wipe the surface of the filter element with a clean cloth to remove any excess filter oil that has not been absorbed.
Reinstall: Reinstall the processed filter element back into the air filter housing, ensuring it is installed properly, and then cover the housing.

Summary:
The best practice for the most common paper dry air filter is to replace it regularly. It is not recommended to try cleaning with water or strong methods, as they have poor results and high risks.

For oil bath reusable air filters, the above steps can be followed for cleaning, drying, and refilling. But even so, there is a lifespan limit, and the filtration efficiency will decrease after prolonged use, ultimately requiring replacement.

Before performing any operation, please ensure that the engine has cooled down and refer to your vehicle maintenance manual. If you are unsure how to operate, it is best to entrust it to professional car maintenance personnel for handling.