K&N Air Filter Installation

Objective: Replace restrictive OEM air filter with high-airflow K&N oil based filter. Allows engine to breathe more freely and increases fuel economy (claimed).

Installation is straightforward, just like replacing the air filter with an OEM one. Remove the intake tube (#12, #14) from the grill up to the airbox by removing the 4 push-lock plastic pins (#15 and #13) with a pair of pliers. Undo the 4 metallic clips that hold the upper part of the airbox with the bottom part. Lift the top airbox assembly and slide the old filter out.

Remove the K&N filter from the factory sealing. Insert it in the same direction as the OEM filter and make sure it sits properly. K&N documentation says that on some vehicles, a rubber gasket may be needed to properly seal the bottom part of the airbox with the top part. On the E46 (and E30) it's not necessary.

Place the top cover in place making sure it seals properly and do the 4 metallic clips. reconnect the intake and secure it back on the car using the push-lock pins. Be careful as they easily break. Now go for a ride and enjoy the slightly louder intake sound.

Cleaning your oil-based K&N filter. Depending on weather conditions, oil cleaning intervals may be short or long. In my country where we have a lot of dust, I decided to clean my filter every year. K&N claims that a bit of dust on the filter actually helps it because it traps even smaller dust particles. For the cleaning process, I got the cleaning kit from K&N and followed the simple instructions:

Spray the filter with cleaner, leave for a couple of minutes to soak

Wash the filter with tap water - not pressurized and let to dry. Don't use hairdryers etc.

Spray the K&N oil on the filter until it becomes red on the entire surface.

DO NOT OVER-OIL THE FILTER BECAUSE EXTRA OIL WILL BE SUCKED IN AND WILL PROBABLY CAUSE PERMANENT DAMAGE TO THE EXPENSIVE MAF SENSOR RIGHT AFTER THE FILTER.

Leave the filter outside the car for a couple of minutes so that possible extra oil drains.