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.
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. 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
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:
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.