Oil on filter?

[Rob S.]

I'm always reading (here) about oiling (the inside?) of pods and perhaps all air filters. I must confess I've never done so. I've always wondered about this.

What is the purpose? To capture more and finer particles, correct? But isn't an oiled filter more restrictive than a dry one?

 

[Grimly]

Depends on the material used to make the pod or foam cover.
Some are dry (paper obviously), but many use a light oil to enance the dirt capturing properties - and a special magic oil only found from the compressed tears of unicorns harvested by dusky maidens at daybreak on the slopes of the Carpathian Mountains, going by the asking price.
Me, I've always used a 50/50 mix of ATF and diesel for my K&N elements and have seen no harm from it.

 

[bwringer]

The stock filter for some GS models is paper, like you see in cars.

In others, it's (lightly!) oiled foam. The proper amount of oil does not restrict flow at all, and it captures dirt particles as the air makes its way through the cells of the foam. Too much oil can indeed be restrictive, so you just need to pay attention and follow the instructions.

Both types of filters are quite effective and are not restrictive if properly designed.

Most dirt and dual-sport bikes also use oiled foam, since the foam can be easily cleaned, re-oiled, and re-used.


K&N filters are oiled cotton. Without triggering the Great K&N Wars, let's just say their effectiveness is variable and controversial. The ones used for pods normally do a pretty good job, but the factory filter replacements are often not that great.