Ask them if they properly oiled it before installation and cleaned them every so often. I've seen people just drop in the filters then wonder why they didn't work, when the instructions clearly state that oiling is essential.

 

Dirt gets on the cylinder, or in our case rotor, wall. Piston rings and seals being imperfect, some of the dirt gets past and gets into the oil. The older the engine, the more likely this is to happen. Thats why oil filters are run, not only to catch bits of metal and rubber from engine components, but to catch dust and other sediment that makes it into the oil via the internal structure of the engine and leaky oil pan gaskets. Not sure I explained that perfectly, but thats the gist of it.

 

Hmm... that is a good question Manntis. Most of my friends know what they are doing, so I have a hard time imagining them making such a simple mistake, but that is possible.

 

Oh OK so you are talking about old engines with worned out seals and rings.

 

You just touched on the one downside- they require maintenance.

 

yup, as opposed to throwing 'em out and getting a new one you hose 'em off and spray them with fresh oil.

 

You should be able to just drop it in when you first buy them. They come pre-oiled from the factory.

 

Not just old motors though. Even new ones let dirt past the seals and rings.

 

I can't see why K&N would lie about this:

Off-Road and Racing Off-Road

An air filter element becomes an insurance policy when used in off-road applications. Competitors will sacrifice a high-tech engine for a chance to win a race — but to win, they must finish. If the engine ingests too much dirt and debris, it may die an ugly death before the vehicle can cross the finish line.

K&N air filters are designed to provide minimum restriction long after disposable air filters have begun choking an engine. In other words, due to its characteristics, the restriction of a K&N replacement filter increases at a slower rate when compared to a disposable filter, i.e. a K&N filter will last longer under the same conditions. That's why most off-road competitors choose K&N filters.