I run the Mobil 1 filter on the GN. I have the biggie adapter so run the larger filter. I found an ebay auction several years ago and got 28 (yes 28) filters for about a buck fifty each! No one else bid. The shipping was almost as much as the final price but who can argue the value. So I got a lifetime supply of filters for way less than 3 bucks each. I am very happy with them.