Second thoughts about K&N

They only make a marginal increase in performance as mentioned at WOT that’s because when clean and properly oiled they are less restrictive however downfall you’re sucking in junk that’s getting by the filter media. I’ll pass no thank you.
 
K&N were developed for Baja Truck racing. Keeping the gritty sand and dirt out and keeping the engine clean enough to extend its life till the next race. Not terrible but designed for a purpose.

I know a few guys with high dollar sand cars (what they call dune buggies today) with aluminum V8s etc and they won't touch a K&N.
 
Lots of confirmation bias but precious few facts. Have used K&N filters on several vehicles w/o any untoward effects.

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I have two precious facts!

If you put a scented oil on the filter, you can smell it, can smell the oil. The fact is, this means molecules of oil are leaving the filter and entering your nose.

Fact #2 is some sensors including MAF, will be fouled by oil contamination and have degraded performance as a result.

You can connect the dots between these two or choose not to based on contrary anecdotal evidence, but why when the correct filter for the engine usually exists. I doubt K&N makes an oiled filter for any application where a dry one does not exist, but even if they do, that's an exception rather than a wise choice.

I have done lots of less than... wise things in my life without any untoward effects, but since hindsight is 20/20, I repeat fewer and fewer mistakes as time goes by.
 
I've said it before, but I'll say it again, it's physics: Flow more air, flow more dirt. There are no magic filters.
Huh? That is not always true. More pleats with a little finer micron filtration, can potentially flow more air and less dirt. That is also physics, not magic. % restriction multiplied by surface area.

At the same time, filter material is inexpensive, so any quality filter can aim for this rather than try to shave pennies off to screw the consumer in the long run. The annoying part is when a manufacturer adds 30 cents more filter material then charges dollars more for that.
 
I had K&N air filters in all our vehicles that I could purchase one for - until 2 years ago when I ran my finger on the inside of the air duct between the MAF sensor and the throttle body on our 1999 Buick Century and our 1999 Silverado. The tip of my finger came up dirty and gritty. I went back to paper filters on everything!
 
I experimented around with different panel filters in my car and seemed to notice a performance increase every time i switched.

I figured the ecu is compensating for the change in air by running rich a bit either way.

Maybe try the k&n next time you have the airbox open and see what happens. You could also use obd2 software to get a better picture of what is going on with ratios if you have the time.
 
A lot of thought goes into the design and function of a vehicles intake. There's resonators to dampen and absorb unwanted sound frequencies at certain rpms also runners along the plumbing to enhance airflow. I would say the oe intake system is a tight system and was designed to run most effectively and efficiently with the setup the vehicle rolled off the assembly line with.
 
I starting using & recommending K&N oiled filters on dirt bikes in the late 1960’s / early ‘70’s. I would never put them on anything else. Especially these days of downstream sensors from the oiled filters. That’s asking for trouble.
 
K&Ns are only good as a rock catcher and a flame arrestor on a raced car or bike/boat. Hence, I feel K&Ns are to be used only on a racetrack, OHV park(with a foam pre filter, dirt bikes and quads get nasty) or the lake/river.
 
K&Ns are only good as a rock catcher and a flame arrestor on a raced car or bike/boat. Hence, I feel K&Ns are to be used only on a racetrack, OHV park(with a foam pre filter, dirt bikes and quads get nasty) or the lake/river.
When I rode motocross we much preferred uni foam filters
 
More BITOG heterodoxy:

Well got curious about the dirty/oily airbox claims from some here so I checked it myself. 2014 Mitsubishi Outlander 75K miles. Have used the K&N since about 10K miles. Recently ~10K miles cleaned and carefully reoiled the filter. A white paper towel demonstrated some (not much) very fine soot, not gritty. Absolutely no trace of any oil. Admittedly I drive in a fairly clean environment but I think the results of this crude measurements don't warrant tossing the K&N. May trade the vehicle in at 100K when the warranty expires so I probably broke even or a bit ahead by buying the oiled filter vice four or five standard paper filters.

K&N.jpg
 
I had K&N air filters in all our vehicles that I could purchase one for - until 2 years ago when I ran my finger on the inside of the air duct between the MAF sensor and the throttle body on our 1999 Buick Century and our 1999 Silverado. The tip of my finger came up dirty and gritty.
Yes, exactly my experience the other day.
 
More BITOG heterodoxy:

Well got curious about the dirty/oily airbox claims from some here so I checked it myself. 2014 Mitsubishi Outlander 75K miles. Have used the K&N since about 10K miles. Recently ~10K miles cleaned and carefully reoiled the filter. A white paper towel demonstrated some (not much) very fine soot, not gritty. Absolutely no trace of any oil. Admittedly I drive in a fairly clean environment but I think the results of this crude measurements don't warrant tossing the K&N. May trade the vehicle in at 100K when the warranty expires so I probably broke even or a bit ahead by buying the oiled filter vice four or five standard paper filters.

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I run them in all 5 of my vehicles with no drama and have done the "white glove" test in the intake tracts/tubes of each with no oil/dirt issues. I think in one of the threads here I posted a pic of it. I've never had abnormally high SiO2 in my UOA on any of them which is often discussed as an issue when you run these. I am on the east coast and generally drive in a "clean" environment.
 
About 20 years ago there was an argument about K&N performance gains in an MB diesel board I belonged to then.
I ran some zero to sixty tests with my 300D 2.5 Turbo on a deserted, straight stretch of country highway.
3 runs with paper, 3 with K&N. No difference. Even allowing for my stopwatch thumb lag favoring the paper filter, the average was the same within a 1/10 second.
Concluded that the paper filter already allowed as much air as the turbo diesel could suck so it made no difference performance wise.
I have a K&N in my Yamaha though.
 
I'm stuck on the injen dryflow & AEM Dryflow as they don't flow as high as the oil, but you don't have to oil them and the maintenance is far easier. The Apexi Powerflow intake/filters started this trend before anyone and I have believed this is the best method.
 
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