K&N air filter issues 2005 E320 CDI
Then I took some CRC MAF cleaner and thoroughly cleaned the sensor. No luck. Finally, I said "what the hell" and popped the old air filter back in. Perfect! It was strong like bull. lol WTH?
http://www.billswebspace.com/AirFilterTest.htm

Coating of the intake would only be caused if you improperly re-oiled them after cleaning. That myth has been thoroughly debunked.
Other than that, I agree, no useful performance gain for street driving. But then also, there's no useful performance gain on the street with performance brakes, suspension, pulleys, etc, but people like to buy them anyways.
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From my prior link: "Compared to the AC, the K&N “plugged up” nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt."
Running a K&N for an excessive time without service (more than 5k miles) causes them to lose what little filtering ability they have as the oil is pulled out of the screen mesh by airflow.
Lets take a look at a your 08 R320 CDI.
K&N $76.
But you will also need a "recharge" kit. $19
Total: $95
Proper filters $41.50
Both claim to last 50k miles, but the K&N has to be cleaned every 5k miles in street use.
The K&N you have remove it, clean it, oil it and reinstall it. About 1 hour.
The proper paper filter you pull the old, toss it, install new. 30 minutes.
That means it will take you 114k miles to break even in cost, it will take 10x longer maintenance time, the K&N is letting more dirt into your engine 100% of the time, and the K&N is not increasing performance at all 99% of the time you are driving.
Last edited by OM617.95; Apr 7, 2016 at 11:07 PM.
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K&N filters are fine, and they don't plug up faster. The author clearly made the test to cause the result he wanted.
ISO doesn't mean a whole lot in the end, I deal with labs all the time, and despite using GLP they get vastly different results.

I've never encountered this personally, and I use K&Ns on all my vehicles.
I have also heard few cases where new filter has been causing troubles, and all fixed when filter brand changed. Personally I use Bosch in my OM648.


I can confirm that our oil company labs & a certain very well known filter company's labs confirm this.

Honestly, I don't think there's any benefit in debating this - the test was clearly set up to debunk performance and efficacy under track conditions, and therefore is irrelevant for road applications.
One of the key claims it makes is that oiled filters will dirty your oil, however, my oil analysis after 18,000kms service on my oil, using a K&N filter, indicated that the oil was exceptionally clean. And based on owning several other vehicles and putting in excess of 300,000kms on them with no signs of unusual engine wear, I see from my personal real-world experience, no evidence of these poor filtration claims.
If I were to hazard a guess, I think AC Delco had some influence in those tests. But that's just speculation.

Last edited by Glyn M Ruck; Apr 13, 2016 at 11:48 AM.








