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Discussion Starter · #1 ·
What are the advantages of a K&N air filter? Are they really "reusable" after cleaning? How does it affect gasoline consumption, engine power output, and longevity of the engine? Is it true what K&N says, that using one will not void the manufacturer's warranty?
 

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You can find the answers to your questions here:
K&N Air Filter Review - Debunking the Myths (and why OEM is better)

The ONLY advantage of K&N filter is lower pressure drop vs. OEM. But this only matters under wide-open-throttle (WOT) conditions, because the biggest pressure drop in the intake system is the (partially closed) throttle valve, not the air system. So unless you drive 90% of the time with your gas pedal firmly pressed to the floor, K&N filter makes absolutely no difference, and has tons of disadvantages:

- Cleaning a K&N filters creates more pollution than disposing of a paper filter.

- It requires much more frequent maintenance than OEM.

- It allows many times more dust into the engine than OEM.
 

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They are what they claim, but IMHO they do not add to performance at all. Just be sure to follow the cleaning and oiling procedure carefully.

Long ago some claimed that the K&N fowled the intake, but that was individual filters on high-velocity carburetors, not the big-box air cleaners on stock Toyota engines. For example, I have a high performance engine with four carburetors (one for each cylinder) and K&N filters were simply not cost effective. The maintenance for such a setup was too much. Paper filters were better. I over-oiled one and performance slipped. (Getting four carbs in synch is difficult enough without adding another factor.)

But again, our big box filters flow plenty of air regardless of stock or K&N filters.
I like to keep it simple and replace using a stock filter.
 

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Discussion Starter · #4 ·

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What are the advantages of a K&N air filter?
Not enough to offset the disadvantages

Are they really "reusable" after cleaning?
Yes... the cleaning/oiling kit is around $20, good for maybe 10 uses.
Make sure you don't need to use your car to allow the filter to dry after cleaning before oiling.

How does it affect gasoline consumption, engine power output
No measurable improvement.

and longevity of the engine?
Potentially reduced engine life due to lower filtration efficiency.

Also potential for MAF pollution due to over-oiling (VERY common mistake)

Is it true what K&N says, that using one will not void the manufacturer's warranty?
Your warranty is in no danger because the manufacturer must prove that the aftermarket parts caused or contributed to the failure.
This will not be an issue because when your engine begins to burn excessive oil due to cylinder scoring it will be long out of warranty.


Want to see what a K&N does to your engine?
Change your oil, install a new OEM filter, drive for 10,000 miles, and send a used oil sample to Blackstone for analysis.
Change the oil again, install a K&N filter, drive for 10,000 miles, and send a used oil sample to Blackstone for analysis. Notice how the silicon levels are elevated, and possibly copper (bearings) and aluminum.

The OEM intake system can flow more air than any normally-aspirated V6 engine can use. K&N has its place on racing engines.
 
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