K&N Air Filter Cleaning and Oiling

As advised by K&N, the replacement drop-in box air filters will require some maintenance in the form of cleaning and oiling every 50,000 miles (80,000 kilometres) or so, but I make it a habit to usually do this every 20,000 to 30,000 kilometres.

drop-in air filter
K&N drop-in air filter for the Alfa Romeo 147

If you had installed the air filter on your own as I did, you would know how to remove it from your car’s air filter box. For the Alfa Romeo 147, the steps are shown here.

If you had this installed at the workshop, the information should be available with your car manual or online. You could get your regular mechanic to show you how to remove it.

However, it would not be feasible for your mechanic to do a complete washing of the filter for you as it would take hours for the filter to dry properly in the middle of the steps.

Unless you’re leaving your car at the workshop overnight or have at least 4 or 5 hours to kill, or have a replacement or the original filter to use temporarily, this job is usually a DIY best done at home.

I usually perform the K&N air filter cleaning and oiling in the evening before dinner, for the reasons as I will explain in the following steps:


Removing, Cleaning and Oiling the K&N Filter

removing car air filter
1. Start with removing the K&N air filter from your car. This should be a fairly simple process, often requiring only a screwdriver or unlatching of clips.
wash air filter
2. Tap the filter lightly on the floor to dislodge any loose dirt and leaves. Be sure not to tap to hard as that could dent and damage the wire mesh on the filter. Identify the clean and dirty sides of the filter based on the flow passage through your car’s air intake. In the photo above, the clean side is above, and the dirty side is below.
k&n air filter cleaning
3. Spray the K&N air filter cleaner generously and evenly on both the clean and dirty sides of the filter. I only have one hand to do this, and the other hand on the camera. Best to do this over wash basin or sink, or toilet floor as I have done in the photo above. Do not allow the cleaner to dry on the filter. Leave it on for about 5 to 10 minutes for the cleaner to penetrate well into the filter and loosen the dirt before proceeding with the next step.
cold water rinse
4. Rinse the air filter with low pressure cool water from a tap and allow the water to flow from the clean side to the dirty side first. This will allow most of the dirt to be washed out from the dirty side below. Once it is a little cleaner, you may turn it around and briefly rinse it the other way round. Apply more cleaner and rinse again if necessary.
k&n air filter cleaning
6. You may also use a shower to rinse, but use only low pressure cool water to avoid damage to the cotton pleat of the air filter.
car engine bay
7. Rinse the filter all over until the oil has been washed away. This will be when the cotton pleats have turned from red to grey or black, as seen above. You will then need to leave this to dry.
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This is when I will have my dinner while waiting for the filter to dry. The filter should be left to dry naturally, or under a fan to speed up the drying process. Avoid using a hair dryer if possible. However, before leaving it to dry, it would help to shake the filter to remove excess water.

I sometimes lean the filter against the wall or with one end on a curb, for excess water to drain off gradually, flipping it to the opposite side every now and then. Way after dinner just before bedtime in about 3 to 4 hours, the filter should already be dry and ready for the next process: oiling!

I could not take any photographs of the oiling work as it requires the use of both hands. So, to continue from where we left off:

applying oil
An idea of how the oil is run along the cotton pleats and not across it.

8. Flip open the nozzle of the K&N air cleaner oil bottle and apply it on the cotton pleat row by row, running the nozzle slowly at the speed of 3 cm per second along the pleat (not across the pleats!) and at the same time squeezing the bottle gently. Apply only on one side of the filter.

9. Allow the oil to seep through the cotton throughout for about 15 to 20 minutes. By this time, most areas of the cotton pleat would be red – the colour of the oil. Lightly drip some oil on any area of the cotton pleat which is still white or grey.

10. Leave the air filter to dry naturally overnight and install it back in your car in the morning.

k&n air filter cleaning
Reinstall the cleaned, oiled and dried K&N air filter into the filter box of your car and you’re ready to go!





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