I thought I'd share some of my practices with regards to BMC filters. This applies to any high flow oiled filter, it just so happens that BMC is my filter of choice for all my vehicles. I'm not saying every person with a filter like this absolutely needs to agree and follow my practices, but I've fooled with enough filters and have cleaned enough mass air flow sensors to feel comfortable on this subject. For all I know, many of you may do this already.

As most know, switching to an oiled aftermarket filter is almost always good for a little more power... and since many of the aftermarket intakes available actually lose power, cause lean conditions, etc., these filters combined with the factory airbox are often times the best way to go. However, many of these filters are over oiled from the factory, even though they claim they're ready to drop in right out of the box.

An over oiled filter can also cause problems by contaminating Mass Air Flow senors (MAFs). Excessive oil gets blown from the filter as the air passes through and collects on the MAF's heated sensing element. If this thin wire gets insulated by oil it is no longer able to accurately detect the actual amount of air passing through the intake. The result is reduced performance, or absolute worst case, a damaged MAF sensor. CRC makes a MAF sensor cleaner that works well if this should happen, but my practice is to avoid any contamination in the first place.

I recommend rinsing these filters right out of the package with plain warm water... almost hot, but so you can still hold your hand under it. This will wash away much of the excess oil on the filter and avoid the chances of MAF contamination. You're not trying to clean it, just remove the excess. There will still be plenty of oil left to help catch and hold those pesky particles.

Below are some pictures I've taken to help show how much excess oil there can be.

Left filter is brand new & fresh out of the plastic, Right filter is brand new, fresh out of the plastic & rinsed with warm water


Up close


Oil left after rinsing one filter


Water drained - wife ready to kill me for making a mess in the sink. Better here than on my MAF sensors!


Just make sure you give the filter(s) plenty of time to air dry before installation.

 

I've got them on my Cayenne for nearly three years now, they sound nice when I rev the car.