Dealers allege that oiled filters foul Mass Air Flow sensors. Ask them to prove it. Ask them if they can test a MAF? They can't, their service info tells them to install the MAF on a like car and see if it works.
They are told this by people who don't want to replace MAF's or don't know how to fix the real underlying problems. I know lots of dealerships who sell and install Airaid kits. One Chevy dealer I was at last week has 10 of these Camaro kits on order.
Here is a re-post of a response I did regarding oiled filters. Check out the K&N link for the independent testing they had done. 256 "fouled" MAF's tested. Check out the results.
Sorry for the rant, but mis-information just pisses me off.
"First. All cotton gauze filters are not the same. Sounds simple but the term "K&N" is like "Kleenex", and gets applied to the category. There are cheaper versions and more modern versions (the basic K&N filter dates back to the early 70"s). Very cheap & offshore versions are easy to identify. Hold them up to a light. If you can see pinpoints of light then dirt will get thru those holes. Any filter is a compromise of Flow vs Filtration. A normally aspirated engine (air pump effect) has a set demand it needs. Lets say 300 cfm. If a filter has a higher airflow rating of 350 cfm, than you are giving up filtration. The motor will pull no more than 300 cfm. If a filter allows less than the 300 cfm, then it would be considered "restrictive" but probably "filters' better. OE's want to make power, long life (100,000 warranty) and keep noise down. They spend lots of engineering money to get an acceptable (in their eyes) balance.
"Wet vs Dry"
The dirt released from the filter comes from cleaning the oil off, which the dust clings to. It's the "release agent". A dry filter is put in a bucket and agitated. You will get the surface dirt out but not the deep dirt. So each washing leaves the filter less efficient that it was new. Think vacuum cleaner filters. It will never be 100% efficient again, a oiled gauze filter is. Again it's Flow vs Filtration. Dry filters have come into vogue due to the great "Oil on Mass AF sensor" debate. Foam filters are synthetic not natural fiber. Oil will not penetrate the foam, it sticks to it. Foam filter manf use a thicker sticky oil to cling, but it WILL shed off. Did we use foam for years on powersports and trucks? Yes, when they were carburated and the motor wasn't affected by ingesting a little oil.
MAF Fouling.
Oiled Mass Air sensors is pretty much an urban myth. Check out the K&N website for the actual scientific testing they had done.
http://www.knfilters.com/MAF/MAFTestresults.htm
A lot of dealers make a big deal about this because they've been scared into it by the warranty techs. Keep this in mind. A GM dealership has NO way to test a mass air flow sensor. The book tells them to put the MAF on a same year vehicle to see if it's bad. !!
Can it happen? Sure. From over oiling. If a cheap offshore filter has oil on the inside of the bag wrapping the filter than it's over oiled. Don't use it. The biggest culprit is the owner reoiling the filter after cleaning. Ever read the instructions before doing it? You oil a small area and let it wick thru the filter for 30 min. You DO NOT try to get the cotton all red in 30 seconds
Several manufacturers now list the amount of oil they put on their filters from the factory. It's done by a computerized sprayer. The amount averages 0.6 oz. Very little.
Current manufacturers of filter (vs re-packers) spent a lot of time and engineering to get the correct configuration to achieve the best Flow vs Filtration AND correct MAF air signal. Number of pleats per inch, pleat depth, all play apart in "straightening the air" as well as filtration. This is an area that very few kit builders (vs filter manf) spend any time. It's usually what fits in the space. IMO it's very important to know who's filter a kit has in it. Did they cut corners there?
Regarding the post about diesel filters. Different animal. A turbo diesel requires 10 times the air as a gas motor. Yet some OE's use the same air box as the gas trucks due to cost and room constraints. The issue of replacement filters collapsing in air boxes is due to using old gas filter manufaturing materials. The turbo diesel was a new animal. Some manufacturers now cover the filter in expanded metal screens (chicken wire I call it) to give it rigidity. This can result in a 30% drop in flow. Doesn't make sense. Some manufactures have switched from the aluminum wire that hold the gauze together to stainless steel and put reinforcing bars in the side urethane panels. This is the difference between "good enough & doing it right."
There are lots of hype, myths and legends out there on the errornet. Also some facts. Do your research from multiple sources."
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