Q – I just bought a Boxster S and it has a K & N air filter. My mechanic said that it needed to be serviced. I wondered what your thoughts are on the K & N versus the factory filter? He suggested that I go back to the original dry filter. Pete

A – Well Pete, if you are the one servicing the K & N and if you have extra time on your hands, keep it and buy the kit to clean and re-oil it. However, for my money, I recommend the original dry filter in your Boxster.

Here is my logic: Considering the time it takes (and time is money when you are paying someone else) the cost/benefit ratio does not work out. To get to the filter alone is a chore. Cleaning it is messy and then you are supposed to let it dry after you clean it. Another disadvantage of the K & N is that is uses oil to attract and trap debris. When you consider oil as a contaminant of the Air Mass Sensor on your Boxster, you need to be careful not to over oil the filter. If you do, the check engine light can set and your car might not run very well.

I have a K & N in my Carrera but that is a different application.   First of all, it is a cone (non original) style air filter rather than the conventional “panel” filter. On my older Carrera, there are also a few other factors to consider. My car does not have the same design Air Mass Sensor so a little extra oil doesn’t hurt it. My filter is easy to access. And when I service it, I can leave the car apart for however long it takes to clean it and oil it.   I usually wait for rainy weekends.

Do the K & N’s really give you more power? I defer to the manufacturers literature on that question and I am sure they can, but here’s the rub. When the filter is buried in an engine compartment, where you can’t see it, how do you know when it is dirty?

The factory dry filter has the advantage of releasing some of the dirt into the air filter housing that it collects while the engine is running. The K & N does not. It just keeps packing it in. I think that the benefits of a new K & N are real, but as it gets clogged with crud, what benefit does it have then? Frequently I find these filters neglected due to the hassle factor. Now if you still want to use the K & N, buy a stock filter and simply swap the two during the cleaning/re-oiling process and take your time cleaning it. – MC