Not my original source but similar data. As you can see oiled air filters are just not as good at their primary function which is stopping dirt. They also quickly become more restrictive to air flow.
Aftermarket Air Intakes/Filters - Do They Work? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
From all the data I've seen there is simply no better filter (oil/air) or fluids (oil/ATF, etc) than OEM Toyota. Not sure where other manufacturers are regarding quality since I haven't had the need to research other manufacturers.
EDIT: I made some wording changes from my original post as I was too harsh in my evaluation. Oiled air filters are not garbage but they provide very little to no real performance benefit at the cost of being less efficient as a filter medium.
Aftermarket Air Intakes/Filters - Do They Work? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
From all the data I've seen there is simply no better filter (oil/air) or fluids (oil/ATF, etc) than OEM Toyota. Not sure where other manufacturers are regarding quality since I haven't had the need to research other manufacturers.

EDIT: I made some wording changes from my original post as I was too harsh in my evaluation. Oiled air filters are not garbage but they provide very little to no real performance benefit at the cost of being less efficient as a filter medium.
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