Paper vs Washable Air Filters

[ken.mark]

I've always heard that washable gauze-type air filters let more dirt into your intake, which is understandable since you can typically see lots of light thru your typical K&N. AFE is probably the best of the washable filters. I've heard that it was started up by former K&N employees with the intent of making better filters. Most BMW tuners now seem to sell the blue AFE filters, which have a 98% efficiency according to the AFE website. The PG7 AFE is intended for diesels and is rated at 99.7% efficiency.

Here's a oil anaylsis filtration test result that I dug up: http://www.cumminsforum.com/forum/general-tech-articles/5053-air-filtration-results-various-aftermarket-filters.html. The oil analysis test results measure how much silicone (i.e dirt) is getting into your oil:

Stock Filter: Averaged 6 ppm
AFE Standard Media Filter: Averaged 15 ppm
AFE PG7 Media Filter: Averaged 10 ppm
Uni Foam Filter: Averaged 10 ppm
BHAF: Averaged 4 ppm

In case you're wondering, a BHAF is a Big Honking Air Filter (i.e. a big paper media cone filter). Here's a link: http://dieseldatabase.com/bhaf-big-honking-air-filter/?id=15. Diesel truckers are obsessed with air filtration because diesels suck up a lot more air than gas-engined vehicles.

So after reading this, I'm thinking of switching to a BHAF. Does anyone know of a BHAF with a 3" intake that would work well with an E36? If I can't find one, I might use a big AFE PG7 3.5" cone filter since it seems to be the best of the washables (they don't seem to make them in the 3" size). I assume that the AFE Standard Media filter is the blue one and it's interesting how vastly the test results vary between the AFE PG7 vs AFE blue when they are 99.7% vs 98% efficient. K&N does horrendously in some of the other tests I've come across. I've only used K&N filters myself, but I think my E36 K&N is going in the trash.

I just did an oil analysis for my S50 325i and I got 20ppm of silicone for < 3000mi on a stock paper filter. However, I did just do a valve cover gasket replacement just a couple of months prior with silicone sealer all the way around the gasket, so that may be impacting my results.

[5OnTheFloor]

How do Amsoil filters compare? I've heard they're much better than K&N and I'm running one

[flyfishvt]

Ive never been a fan of washable filters. Thanks for the documentation that supports that opinion. washable filters require oil to work correctly. Too much oil will contaminate your MAF. Too little causes poor filtering. Ive never seen a decent set of instructions on how to tell exactly what is the correct amount of oil to use or how to tell.

Paper filters are cheap and easy.

[JDStrickland]

I had a washable filter on an offroad Jeep, my experience is that it is only useful to save on the cost of replacing filters. For highway cars, I'd stay with a paper filter. You will not replace a paper filter enough times in your lifetime to offset the cost of the washable filter. And you will not notice any performance gains because street driving simply does not afford the time or space to put the car to work hard enough to notice the change in the intake. The oil from the washable filter also contaminates the MAF, so there is no upside to making the change.

[ken.mark]

How do Amsoil filters compare? I've heard they're much better than K&N and I'm running one

Better, but not by much:

FILTER % Efficiency

AC Delco OE 99.93%
Baldwin 99.72%
No name filter (made for gas engine, 1/3 less pleats) 99.32%
AFE ProGuard 7 (73-10062), panel filter 99.23%
WIX/Napa 99.03%
Purolator 98.73%
Amsoil, new style 98.63%
UNI 97.93%
K&N 96.80%

Additionally, these 2 were tested using FINE test dust. The K&N was cleaned and retested, the AFE was the conical version:

K&N 89.85%
AFE Conical 92.33%

This was from http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=492919. I assume the AFE Conical is the blue. Another reason why I would only use an AFE PG7, which does much better. The only problem is that the PG7 doesn't flow anywhere as good as the blue, so you would need an oversized PG7 to realize any improvement in flow.

Here's a visual test result for AMSOIL:
http://www.bobistheoilguy.com/air-filter-filtration-test/

[scooper]

I've been using an Amsoil air filter (big ass one at 9" and 3.5" diameter) but I may be downsizing because I'm doing a headlamp upgrade which takes a little space. The filter sounds great.

I'll put the 9" up for sale in June when I do the headlamp upgrade if anyone is interested. Includes the appropriate Amsoil pre-filter.

[BMWMPow3r]

good thread.

[JDStrickland]

Modifying the air filter on your daily driver is a waste of money. Buy your wife some panties and bra with holes in them, you will get far more enjoyment for the investment.

[Kody]

Ive never been a fan of washable filters. Thanks for the documentation that supports that opinion. washable filters require oil to work correctly. Too much oil will contaminate your MAF. Too little causes poor filtering. Ive never seen a decent set of instructions on how to tell exactly what is the correct amount of oil to use or how to tell.

Paper filters are cheap and easy.
I've never had a problem with my oiled filter screwing with the MAF and I put about as much oil on it as it can hold lol

[Alan777]

I dont see the reason to buy a K&N/oiled filter. No SOTP difference, and they're expensive and kind of a pain to clean/re-oil. It's much easier to just throw a paper filter in.

[ken.mark]

True, an oiled filter on an otherwise stock car is wasted money, but it does make some nice burbling noises when you get on the gas. If you do intake, exhaust and chip, then there is a noticeable back of the seat improvement. Any of those mods on their own is wasted money, however.

[Kody]

My air filter was $15!! Cone shape filter called kool blue. I really like it sounds awesome. Another thing I like is that the end of the filter is open as apposed to a plastic cap. (Open meaning there is filter element at the end instead of being capped off)

[mwood]

its "silicon" ( dirt/sand ) not "silicone"