In the time of pre-internet, I used to use Fram filters exclusively. But after I saw the comparison that showed how bad Frams were, I switched to AC-Delco (which was highly rated.........~15 years ago). When I couldn't find an AC-Delco filter for my application, I chose Wix or Purolator. IMO, the K&N, Bosch and Royal Purple type filters are over-rated and over-priced and are relying on brand-association to sell the product (although I still think K&N's air filters are superb). While I have not attempted to keep current w/ the current production units of the various brands (or the now numerous "reviews" of them), I'm sticking primarily w/ AC-Delco (although I now use Wix for my Olds since its really hard to obtain AC-Delcos for that for some reason....nothing like feeling abandoned by the mothership).