I too have used K&N for years and I have them on all my vehicles now. Have never had any problems with piston ring wear. I have 212,000 miles on my '87 Ranger project truck (2.9 V6 original engine that will be swapped for a 302 this spring) and have had K&N in it for a little more than 3 years. It doesn't burn a drop of oil. Sounds like they work pretty good to me. When I got my '99 Explorer it was getting right at 18 mpg (hwy). I installed K&N filter and changed to Modil 1 oil. I now get just over 23 mpg (hwy). I'll keep my K&Ns.