The Amsoil filter is a thick layer of oiled foam rather than a thin layer of oiled reinforced cotton fiber like the K&N. The filtration principle is different. Oiled foam filters have millions of bubbles that form wide, but highly convoluted passages that allow air to move from the dirty side to the clean side. Dirt particles in the air, regardless of size, tend to move in straight lines after they enter the pores of the filter. Once they hit the oiled rubber, the particles are trapped in the oil film. As a gas, air can make its way through the twisted passages formed by fused bubbles to get to the other side of the filter without much restriction. The K&N uses more of a single pass approach to trap dirt particles. The filter develops a static electric charge as air is sucked through the pores at high velocity. This causes particles that are not trapped directly by the oiled surface to be deflected to the sides of the pores where they get trapped in the oil film. Only problem is that K&N seems to have some quality control issues and some filters come through with many very wide pores that allow some dirt to pass through. I’ve had some good ones and some bad ones in my cars over the years.
I use the Amsoil filter in my truck now because I am more concerned about good filtration than maximum air flow (although the air flow is at least as good a new stock filter) since I live in an area with lots of very fine dust. I’ve had excellent oil analysis results once I learned how to properly oil the filter (wash in detergent, rinse, air dry for 2 day, use exactly 1/3 of a bottle of oil, drain on a paper towel for 2 days). There is no oil residue on my turbo blades or inside of the intake tubing. The Amsoil oil seems to be thicker and has more tack agent than the K&N stuff. So if you don’t have oil dripping off the filter, none seems to get sucked into the turbo or intercooler.
BTW, I don’t sell Amsoil.
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