K & N's are supposed to run better if dirty.
Right from the K&N website
How do I know when to clean the filter?
The general rule of thumb is that the filter needs to be cleaned when the dirt build up gets as thick as the wire mesh. The usual interval is 30,000 - 50,000 miles depending on driving conditions. We recommend that you check your filter about once a year in normal usage.
If it's a daily driver than you really have to go by how it looks. If it looks dirty than it is dirty. Clean it,but when you re-oil it do not over oil it. I notice that when these filters are on Mustangs they don't like a lot of oil where on Bow Tie cars they like more oiling? Don't ask me how I know,I have just had experience with both!
K & N's are supposed to run better if dirty.
Right from the K&N website
How do I know when to clean the filter?
The general rule of thumb is that the filter needs to be cleaned when the dirt build up gets as thick as the wire mesh. The usual interval is 30,000 - 50,000 miles depending on driving conditions. We recommend that you check your filter about once a year in normal usage.
K & N's are supposed to run better if dirty
the dirt buildup in the oil is supposed to be good for KN's.
I'm really having a hard time understanding how a dirty filter works better (with everything else being equal and normal - ie: let's not talk about an over-oiled filter as obviously that's not normal.)
Logic tells me a brand new or a non-damaged, well cleaned and oiled K&N filter (again, let's be sure we are comparing apples to apples) will flow better than a "dirty" filter or a filter with "dirt buildup".
FWIW, I clean and oil ours once a year.
Fuel Injection Performance KitWhile were on the subject of K&N...what does "FIPK" mean? This has been buggin me for the longest.
Dirty filters "trap" more particles because it has something to grab on to.