The only sure way to tell is to do an oil sample. Pull a sample before you install a K&N then do one after 5K miles or so after installing it. Blackstone offers the kits for free, then when you send it in it costs about $20 to have it analyzed. This will tell you for sure if you're doing any damage to your engine, of which I would be surprised if you do. Go to
http://www.blackstone-labs.com/ and order your free kits if you want to know for sure what's going on in your engine. Heck, it's a good idea to do one every now and then just to keep an eye on things internally.
I've attached one of the oil sample sheets from Blackstone on a truck I used to own. I ran a conical high flow filter in this vehicle that was the same oiled gauze that the K&N is made of.