If you're talking about a foam filter you need foam filter oil, which is gooier than the K&N filter oil, which is designed for paper element filters. You can get Belray, Klotz, NoToil and others...
It would have been a stupid question if you had put the K&N oil on first, then asked..
Sure dude, experiment all you want, it's not as if you're flying a plane and it's going to crash 'cause you used the wrong filter oil.
Actually, I think the benefit of using the foam filter oil is that it's super gooey so dirt and bugs stick to it rather than split up into smaller bits and get through. Also they can sell you the special cleaning solvents that you will need when it comes time to clean it.