I bought a couple Wix filters from Amsoil's website ($12.70 each, guess I got ripped off). I ended up buying 10 quarts of oil and two Wix filters for my next two oil changes...figure I'll just keep whatever they don't use out of the fifth quart and have them start with that one for the next oil change, and if I end up with one left over, that's just one less I have to buy next time...