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2010 Forester
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Discussion Starter #1
How's it going everyone? I did some research on K&N air filters and from what I've read they are top notch. The company explains that using their stock replacement air filter will not void the factory warranty. The filter has a 1,000,000 mile warranty, it is advertised to increase mpg and horse power. So I am thinking about installing one. Has anyone else put a K&N air filter in their Forester? Please share your opinions & facts. Thanks in advance!!

Best regards,

Otulp
 

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2008 GRB 20th anniversary 6 MT
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6,570 Posts
They provide a little better air flow than the OEM one but less filtration.
I have read a test sometime ago in NASIOC and regarding filtration properties the Sti panel filter was the best (no wonder it is used in GrpN cars) followed by the OEM one, then the K&N equivalents.
It depends what is most important for you 1-2bhp more or better filtration.
I prefer the 2nd :)
 

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2010 Forester
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217 Posts
In addition to the good info that fpan mentioned, if you decide to go with the K&N setup, be careful when applying the oil -- too much will eventually foul your MAF sensor ($$$), too little will decrease filtration. Personally, I don't have the patience to clean/oil these filters when needed and to also make sure I properly oil it, so I'll stick with the OEM replaceable filter.

Regards,
paul...
 

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... it is advertised to increase mpg and horse power...
Actually, the last time I visited their web site I could find nothing about an increase in mpg.

I believe the MPG increase claim is absolutely false (although popular), and they could be sued if they in fact made such a claim.

Think about the function of the throttle plate in any engine. It's purpose is to RESTRICT air flow and thereby control the speed of the engine.

Without trying to describe it in detail, if you think about trying to hold a given engine speed with two different filters, the same total restriction of airflow will be required no matter what type of filter is used. The trottle may be in very slightly different positions because of the (negligable) difference in flow through the filter, but the the total amount of restriction, and air flow will be exactly the same in both cases.

The only time that the filter can make any difference is at full throttle, and how much total time do we run at fully open throttle ??

My $0.02...
 

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2010 Forester
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Discussion Starter #5
That's for the opinions and facts. I don't think I'll be doing it. I must have missed the part about having to oil the filter.
 

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I run a K&N in my 09 XT, really doesn't do a whole lot for performance or MPG.

What I'm going to do is get a Perrin Cold Air Intake, that WILL provide more power.

Close cell sponge like filters like Perrin's cone filter allow more air to pass though, but that's also because the filter isn't inside a small box...like the K&N goes into.
 

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2009 Forester XT 4EAT
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Ok, here we go again.... :shake:
First off, search the forum here and you will find many upon many arguments about pros and cons of aftermarket air filters including K&N.
The better or less filtration argument has also been cussed and discussed at length in the forum here.
I have used K&N filters (both air and oil) since I have been able to drive (1983).
Yes, K&N air filters use a special oil to wet the filter media which helps in the filtration. Is it difficult? Not really. Pay attention to the instructions provided with the "Recharge" kit (about $9 at most auto parts stores) and you shoudn't over oil it.
If anyone has questions or doubts about how well it filters, consider looking in the post for Blackstone Results" an dyou will find that my '09 XT with the drop in K&N has the same or lower amount of Silicon in the used oil analysis than anyone else that has plunked down $28 for the test.
The main reason that I have used K&N in all my vehicles over the years is that I don't like using a filter and throwing it away. (I currently have a '98 Dodge Ram 1500 5.9 magnum with over 300K on the SAME K&N filter.)
There are other's out there, look at them, compare and decide for yourself which one fits YOU. That's the best advice I can provide.
Happy hunting! :biggrin:
 

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2009 Forester XT 4EAT
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By the way...I almost forgot...
Welcome to the forum. I didn't mean to be grouchy in the last post, but you can find an entire WORLD of information on these pages.
Search the forum and you will literally find tons of information about filters (oil and air) as well as types and brands of oil, lubricants, tires...pretty much anything you could want to know.
If you don't find it in a search, ask online and I am sure one of us will have some answers for you.
Again...welcome to the family!
 

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2011 Forester XT 4eat
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By the way...I almost forgot...
Welcome to the forum. I didn't mean to be grouchy in the last post, but you can find an entire WORLD of information on these pages.
Search the forum and you will literally find tons of information about filters (oil and air) as well as types and brands of oil, lubricants, tires...pretty much anything you could want to know.
If you don't find it in a search, ask online and I am sure one of us will have some answers for you.
Again...welcome to the family!
Sure Welcome but its on every forum a lot. If you can't check an air filter just bring it to the shop more often.

I've had very good experience with K&N but... It won't save you on fuel unless you are going to keep the car for 50k. It doesn't really add power well maybe a little. It does filter really well and any idiot can do it properly.
 

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2019 3.6R & 98 Forester Atlanta, GA
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If you have a chance hold a K&N filter up to a light. Then do the same with a OEM filter. I used to be a K&N fan until doing this simple test.
 

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2010 Forester
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Waste of money. Extra work. Forget the power increase or fuel milage claims. Your engine will wear quicker since more dirt will get through.
 
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