What prompted me to post this,
In a previous post I made the comment that the K&N filter is one of the worst filters you could put in your car.
Sure it flows more but why. The only way a filter can flow more is to make it more porous, which in turn will allow more dirt to get by.
The Subaru EJ25D engine that I have has over twice the HP that the VW engine has, so trying to gain a few extra HP through an air filter is not a big deal to me. Getting clean air to the engine is.
I've been playing around with my scan tool and have learned more about fuel trims.
I had a K&N filter on my car but have since changed it out to an OEM setup (OEM filter and box). Before doing this the fuel trims were making a 5%-7% adjustments to get the perfect 14.7:1 air to fuel ratio.
With the OEM filter setup the ratios have dropped to 1%-3% adjustments.
Living in the desert we see a lot of dust and I'm in no hurry to ruin a new engine from dust getting by the air filter.
Also there is a chance if you over oil a K&N filter it could ruin sensors (if your engine is equipped with any).
So there you have it. The reason why I posted this info.
For me I've been using Wix Filters on everything I drive.
I use to work in construction and most contractors used these filters (air and oil) on their earth moving equipment. I figured if they used these filters on their million dollar equipment its more than adequate for my vehicles.
