Why I don't like K&N filters or ANY of the cotton gauze filters

[Sentientbydesign]

In another thread I was asked why I didn't like K&N filters and there was a misunderstanding about HP losses with the K&N filter.

Here is my reasoning for not liking cotton gauze filters. Most of it is based on logical opinions or reviews found on the internet. Though my opinion can't be firmly planted in scientific evidence, there are enough reoccuring reviews to qualify (in my mind) that these filters are in fact bad for our cars.

1) I don't care what K&N said in their "independent" lab test regarding filter oil and MAF sensor failure. The fact of the matter is, the oil WILL redeposit itself down stream of the filter if it is too heavily saturated. If they can't design a product that doesn't allow for such a great margin of error when the customer cleans the filter, then there is a problem.

It's not a Segway, I shouldn't have to go through a class to clean and re-oil my filter. FAIL!

This redeposit issue can mean that the MAF gives off false readings, fails all together, or that you just have a dirtier than normal intake path.

2) By design, the cotton gauze has relatively large orifices when clean. Large enough to be seen through with the naked eye. Try doing that with a paper filter. I can almost guarantee you it won't happen.

These "holes" are a great place for dirt (which includes small rocks) to pass through and enter your engine. I don't know about you, but I personally don't like the idea of little abrasive rocks in my engine.

I read a story online regarding someone in the race industry (Nascar maybe?) who used K&N filters and kept having to rebuild heads every 800 miles because the leak down numbers were horrible. They finally went back to a traditional filter and the leak down numbers actually went down from the unbroken in numbers (this was attributed to piston ring seat).

The filter doesn't reach it's maximum filtering capability until it's gotten dirty enough to essentially clog some of the holes. Now your flow rate is probably closer to that of a paper filter or worse.

3) Maintenance- Brush, soak, rinse, dry, oil, dry, oil, dry

This is annoying and takes forever. I have to wash these stupid filters over night in order to have them ready the next day. If the weather is cold, forget about it.

My personal solution would be to look into some of the reusable synthetic filters. My personal favorite in aftermarket filters is AEM. Their dryflow filter has awesome filtration with no oil and no "holes". The filters are a little pricey, but I've used two of them and they've held up very well.

Maintenance includes washing them, then drying. Still annoying, but they seem to stay cleaner longer than the K&N which actually accumulates dirt (it has to...that oil is sticky). The synthetics can actually be tapped gently or lightly brushed to get most of the large particles out if you don't have the time for a full wash.

I believe Amsoil also has a line of synthetic filters, though I haven't looked into them.

[SVTCOBRA]

I've been leaning away from K&N due to similiar stories that I've been hearing.The only car that I have now with one is the Max and I've got a Wix that will be going in it before she goes back to ASU. With my discount at Napa they are less than $5

[BrandAidDesignG35]

Very enlightening Nate, I have K&N in my altima, 'bout time to get a new one - lol!

My Fujita is due to be replaced as well, I have some ideas, we'll see what I come up with.

[joe603]

I've run K&N for years (10+) without any problems on any car. If you spray the MAF sensor with cleaner when you clean your filters, you'll never have a problem.

[Sentientbydesign]

I've run K&N for years (10+) without any problems on any car. If you spray the MAF sensor with cleaner when you clean your filters, you'll never have a problem.

I'm not trying to find followers, just explain my POV. I doubt you've done leak down tests to see how much compression is being lost due to particulates getting through the filter.

On a side note, IF a filter fails to filter well, then your oil will likely get dirtier faster.

[pfarmer]

I'm not trying to find followers, just explain my POV. I doubt you've done leak down tests to see how much compression is being lost due to particulates getting through the filter.

On a side note, IF a filter fails to filter well, then your oil will likely get dirtier faster.

Problem with the leak down test is that it will not tell you how much compression is being lost due to particulates getting through the filter or even if the filter was taken out completely.

Perry

[Sentientbydesign]

Problem with the leak down test is that it will not tell you how much compression is being lost due to particulates getting through the filter or even if the filter was taken out completely.

Perry

True, but making a claim that one has had no problems in 10+ years is a misnomer because it asserts that all of the vehicles with a K&N filter installed were just as "healthy" as a comparable vehicle with a paper or synthetic filter.

The leak down test was just one "test" that I read about that showed consclusive evidence.

[pfarmer]

True, but making a claim that one has had no problems in 10+ years is a misnomer because it asserts that all of the vehicles with a K&N filter installed were just as "healthy" as a comparable vehicle with a paper or synthetic filter.

The leak down test was just one "test" that I read about that showed consclusive evidence.

The point is that it will not show conclusive evidence. It will only show that you have wear on the rings or cylinder that causes a 'leak down'. Any number of things can cause this.

I have over 150,000 on my 99 300m with a K&N filter, uses no oil, gas mileage the same as always, no indication of any issues at all. But that doesn't mean I think the K&N is the way to go especially on a newer car yet where issues with the oil coming off the media can become a bigger issue than on my 300m.

Like I stated in my above post it will start out slightly better in air flow, slightly worst in filtering, then it gets better at filtering, slightly worst in air flow. Over the life from the independent test on the BMW subject car, the end result was the OEM filter did better on average.

I would go with a dry filter. What I have seen from experience with the K&N is that most tend to over oil the filter and often take a shortcut in cleaning and what they use to oil it with. But that aside a good dry filter will probably outperform it over the life of the dry filter as long as the surface area of the media is what is often present in the dry filters.

Perry

[kmckis1029]

i probably under oil my k & n filter... cause im also scarde of the oil leaking... but my g35x has a better sound with the k&n filter... which lead me to believe im getting more air in the engine... with all the bad press i hope im not getting more air at a cost of filtration... but i been running the filter since i brought the car almost exactly a year ago... my gas milage has been the same... then if it is leaking and dirtying my oil, it wont have a chance to really matter cause i change my oil so much...

i guess my point is I think this will mater more to the people who have longer maintience intervals on their oil/fluids and filters on their car...

[pfarmer]

i probably under oil my k & n filter... cause im also scarde of the oil leaking... but my g35x has a better sound with the k&n filter... which lead me to believe im getting more air in the engine... with all the bad press i hope im not getting more air at a cost of filtration... but i been running the filter since i brought the car almost exactly a year ago... my gas milage has been the same... then if it is leaking and dirtying my oil, it wont have a chance to really matter cause i change my oil so much...

i guess my point is I think this will mater more to the people who have longer maintience intervals on their oil/fluids and filters on their car...

It isn't your oil you should be worrying about, it is your engine. if the filter is causing your oil to get dirty then your engine had to pass that dirt to the oil.

Perry

[Sentientbydesign]

It isn't your oil you should be worrying about, it is your engine. if the filter is causing your oil to get dirty then your engine had to pass that dirt to the oil.

Perry

What he said ^^^

This can be tested, but I won't be doing it lol. It's very possible to run testing on the same engine and do oil analysis to see how much silica (I believe) is in the oil or in the oil filter when comparing a paper filter to a cotton gauze design.

Then the engine could be torn apart and analyzed for scarring.

On a side note, I thoroughly believe that intakes can make a difference with throttle response and to an extent power (more so, they can be designed to prevent a loss of power from heat), but they usually just provide sound.

[pfarmer]

What he said ^^^

This can be tested, but I won't be doing it lol. It's very possible to run testing on the same engine and do oil analysis to see how much silica (I believe) is in the oil or in the oil filter when comparing a paper filter to a cotton gauze design.

Then the engine could be torn apart and analyzed for scarring.

On a side note, I thoroughly believe that intakes can make a difference with throttle response and to an extent power (more so, they can be designed to prevent a loss of power from heat), but they usually just provide sound.

Most put them on for the noise factor, but I agree they can be designed for power such as the ones on my 08. Can you get some more, most likely but often not in the way most think. I looked at the carbon fibre one posted awhile back and the first thing most seem to look at was how it wasn't as smooth inside as expected. Well sometimes smooth is not what you desire when it comes to something like an intake. It is possible that the designer actually created it this way to create a boundary layer on the tube which actually can increase air flow. Without some special equipment we would not be able to test this to see if this designer really was sharp or simply doesn't know how to make a smooth tube.

One point I wanted to make about the leak down test is that some leak down is normal and the rate can vary greatly (and should based on type of use). For example on a passenger car that is not to be raced then you will often have a much tighter leak down then one that will be raced due to expansion considerations for maintenance of piston ring gap. Typically the higher the heat load the greater the need to allow expansion. Hence at rest which is where the leak down test takes place, an engine built for high performance may show what may be considered unacceptable leak down for a passenger car.

Also it is possible that a leak down problem really is an issue with break in procedure or poor ring location during a rebuild. I am not sure of exactly how many rings are present on the 'G' but I can tell you with certainty that it is possible for the stars to line up so to speak with gaps.

Perry

[kmckis1029]

this is all very interesting... one of my friends just got an 2006 RL with SH-AWD and he was scarde to use a K&N filter... he had just brung up this same conversation like 4 days ago... then i log on to g35club and yall talking about it...

I just know i havent had any problems and when i installed my 5/16th spacer there wasnt much of any oil on my upper or lower plenum... or even in the intake track...

but i have been looking into getting a dry or synthetic filter just out of pure laziness of not wanting to cleaning an oil based filter.

While i believe the problems yall describe are real... i just wonder how frequent the problem really is... i mean k&n should be out of business by now if oil is leaking in your intake track and the filter is allowing dirt into the engine... especially the VQ engine which is sucking every bit of power from a v6... it should be very noticable with our engine's tight tuning...

but this is great info never the less... keep it coming.

[pfarmer]

this is all very interesting... one of my friends just got an 2006 RL with SH-AWD and he was scarde to use a K&N filter... he had just brung up this same conversation like 4 days ago... then i log on to g35club and yall talking about it...

I just know i havent had any problems and when i installed my 5/16th spacer there wasnt much of any oil on my upper or lower plenum... or even in the intake track...

but i have been looking into getting a dry or synthetic filter just out of pure laziness of not wanting to cleaning an oil based filter.

While i believe the problems yall describe are real... i just wonder how frequent the problem really is... i mean k&n should be out of business by now if oil is leaking in your intake track and the filter is allowing dirt into the engine... especially the VQ engine which is sucking every bit of power from a v6... it should be very noticable with our engine's tight tuning...

but this is great info never the less... keep it coming.

Infiniti is probably a very small potato for K&N. Again to me what is important is how well over the life of a filter it functions regardless of type. It would be interesting to know how the stock filter compares over time in the way of average air flow and average filtration.

Also if you really want the cleanest oil around, consider a partial bypass design which would allow much finer particle removal. However it comes with a risk, that of a minor failure become a much larger failure before the average driver will detect it.

Perry