I have an 01 Tundra and after hearing and reading about the great benefits of the K&N and Amsoil air filters I purchased an Amsoil dual oil/foam air filter that they claim is superior to the K&N oil/cotton air filter. I had previously been told that there is no - none - nuca - nadda - premium oil/foam/cotton air filter currently on the market or in a development stage that will keep dirt particles out of your engine as well as paper air filters. The oil/foam air filters will allow at least 30 times more dirt to enter your engine. Well, I went with the propaganda/marketing and disregarded educated advice. I sent an oil sample into Predictive Maintenance Services in Uhrichsville, Ohio for piece of mind two weeks ago - well now I've got a case of the a*s as the results show that my silicon content is a whopping 59 - it should be in single digits!!!! I immediately checked my induction system for any leaks or any signs of a previous leak - checked out perfect, no leaks - My iron is at 16, copper is 34, tin is 4 and aluminum is 3!!!! What that means is the damn dirt is acting like a lapping compound causing high copper (34, should be low single digit), Tin (4, should be lower or 0), Aluminum, as these softer wear metals are immediately being affected by the abrasive (dirt). An in-law of mine ran the K&N on his Dodge diesel and went back to factory paper after he got his oil analysis back. I just smiled because I told him to go Amsoil - who's laughing now? I guess the experts are right - you can have either good air flow or good dirt blocking performance BUT not both from one air filter - your choice - I'm going back to factory paper today.