OT : K and N air filters for cars

Are they really as good as advertised? Does anyone have long term experience with them?

K&N Feedback
Hey String!

I have had a K&N Air Filter in my Dakota 4X4, with the 4.7L V-8 for the last 4 years. I didn’t notice any real increase in fuel milage, but I use it for towing my camper. I do seem to feel a little more power going up the hills when towing my camper. I also bought it knowing I would never have to replace it, meaning money saved over many years on replacement filters. I normally keep a vehicle a long time.

Where I really noticed a difference is in my 1996 Mazda Miata. This car is stock with a double overhead camshaft 1.8L engine, putting out 133 HP. I really noticed a big difference in Throttle Response. I noticed the car responds a lot quicker when giving it gas, and it seems to have more power when the motor is wound up producing peak hp. It made a noticable performance difference in this car.

If you are buying it for a “family car”, just driven back and forth to work, you probably won’t notice much difference, except for a long term savings on replacement filters.

But if you are buying a K&N air filter for a work horse vehicle (like my truck), or a performance car (like my Miata), I think it is a worthwhile expense.

Ask if you have any questions!

Hi String
I was interested a few years back and did some investigation. I don’t remember the figures but an independant report of tests conducted on twelve cars and trucks showed scattered results. Several cars got a little better milage some got less. Dyno results were more lope sidded. I will have to look but my recolection is that one car demonstrated more horsepower or torque, and the rest were less. I had a 03 Vette at the time and it’s power deltas were the worst of the bunch so I did not get it.

The one real advantage which may make them worthwhile is that you can clean and reuse the filter elements.


Cleaning and re-oiling
is just another maintenance task to put off. Lot easier to just replace a paper filter :slight_smile:

If You Do, Remember
I think I got some performance improvement in my '86 Toyota Tacoma with a 2.4L inline four. I really don’t pay much attenion to gas milage.

If you do get one, remember to clean it at regular intervals. It will get clogged just like a regular one,and if it is not cleaned it will just be counterproductive.

Cleaning is important
K&N states that you should be able to go 50,000 miles between cleaning. I do a mobile oil change service and yesterday I just removed one from a 2003 Chev HD diesel. Not my truck. It didn’t look very bad but was the first vehicle in 3-4 years that the reset indicator on the breather was almost maxed out. Note, this was just a drop in, not the full plenum duct version. Also several service centers don’t recommend them.


So there is a good chance that I fell
for a sales pitch.

It definately increased the power, esp. on the low end.I was hoping for better mileage. Time will tell.

I believe I remember reading in sombodys annual report that K&N is the largest aftermarket air cleaner supplier.


some swear by em
some hate em. I don’t like the open pore paper sytem they have. I feel too much debris gets into the engine, for the trade off of maybe 5-7% HP gain if any. Just my personal opinion, but I have worked automotive service for 8 yrs.

use K/N in the RV
for a while (RV has Duramax/Allison) but didnt like the oiling process so am now using an AMSOIL filter requires no oiling.

K&N filters
I had used these on my motorcycles for years, so when I got read to put my '94 Dodge van, 3.9L V6 back on the road after a complete engine rebuild, I put in the K&N filter.

I did not notice any change at all until after I replaced the muffler with a 2 chamber Flowmaster unit.

The throttle response increase was DRAMATIC!

Of course, the exhaust note climbed a few db, also! :slight_smile:

The van has an automatic tranny, and several people who drove it absolutely scared themselves when initially getting under way.

Remember that your IC engine is basically an air pump, so the more efficient you can make it, the better it works.

Reducing the restriction on the intake side without a corresponding reduction on the output side will yield minimal if any results.


I can feel the difference in power,
but the truck was no slouch to begin with. However, I got it because a friend told me it increased his mileage 2-3 mpg.My first half tank showed a drop of 1-2 mpg.

Could that be
from making use of the power increase (as in “heavy foot”)?


Nearly 400k
On my cummins using K&N. They have their issues, and need proper care. Not good for non-anal mechanical folk. I’ve had good luck, but probably regular filters would have been fine as well. Engine is turned up a bit.

I quit using mine

– Last Updated: Dec-15-05 10:28 AM EST –

after the oil migrated off of the filter and trashed the EGR valve, $450. My mechanic shop said that it is not uncommon for this to happen. I do electrical and mechanical maintenance for a living and kept up the filter per manufacturers recommendations, even going light on the oil as they caution against using too much. The tiny HP gain isn't worth another EGR replacement. We have to use an ethanol blend fuel in the winter here in the Denver area. I notice more HP difference between summer/winter fuel than I did with the K&N. Ethanol has less BTUs than gasoline. Consequently, I get about 3mpg less in the winter from having to push the gas harder to get there. EPA is considering lifting the requirement because modern vehicles put out so much less CO and particulates that it is hardly worth it from a clean air standpoint. More than you asked for, but it's interesting just the same.

A K&N filter has always been the first
addition to my motorcycles. Mainly because the cost of replacement was much less (over time)than the cost of oem. I put one on my 95 Jeep Wrangler. 4 cylinder, manual trans. It did really seem to improve throttle responce but I noticed no mpg change. The jeep needs a supercharger now, 165000 miles and I can’t maintain 70mph with both a canoe and a kayak on the roof!

My Beemer
a 1978 R80/7 has had one all of it’s life. But, it doesn’t have an EGR or any other emissions garbage either. The Dyna III electronic ignition was worth every penny, too. Oops, I should be posting this on Airhead Beemers Club…


Sing, I’m a lifetime professional mechanic. In my oppinion they aren’t worth the bother. The maintenance is a pain and if done poorly they will coat your air mass meter and intake temp sensor with the special very sticky oil. The outcome is you walk. As for milage increase, it’s hit and miss. Air filters are so cheap.

they may increase the output of an engine a small amount when properly maintained, often the filters are neglected or even worse- overly maintained.

The oil placed on the filter commonly makes its way to the mass air flow sensor, which skews the true airflow readings. This causes a notable reduction in performance.

A mass air flow sensor commonly retails for $400-$600 +labor. A disposable air filter averages about $8.

I would suggest sticking with a disposable paper filter.

that the EPA would look at lifting it. Here in the farm belt, ethanol is getting a good amount of support. I service a fleet of govt vehicles that is running E85 (85% ethanol) vs the common E10 that is being used in the smog control areas.

Performance and milage are both down, but I see it as a positive way to reduce our need for oil and perhaps draw some interest back to the lost art of farming.