K&N Filters

It was no problem to install on my 2003 Forester XS. Gas mileage went up almost 1 MPG, but that could have been due to break-in, as I installed the filter pretty early in the life of the car.

There has also been discussion on some of the Subaru Web sites about Green Filters as another alternative.

Dennis Maher wrote:

I installed it on my 2002 Outback STW. Really easy do it job.

One problem, though. After installing it I noticed engine knock/detonation (ping). Went to my service shop and decided to take it out in order to reduce it.

Yes, car was a little bit more peppy, but it was taking more gas as well.

Voja

Dennis Maher wrote:

How long was it in? A little more time might have cured everything. Changes in the intake need time on modern OBDII cars. TG

I have installed "short ram" air intake with K&N filter on my '97 OB. I have reset computer by disconnecting battery for more than one hour (during installation), and it took more than 1000 miles before my computer adjusted MPG back to value I had before installation. I got a little performance increase at 2500 rpm and higher, but my transmission started to "think" before changing a gear. Now, after 3 monthes with K&N I switched back to original plastic air intake and original filter to see difference...

I have a drop-in K&N in my GT wgn and noticed in the first week that it does pull a wee bit harder and more smoothly (it lessened pings and low rpm hesitation) and may have helped mpg a bit as well. I got a highest of 28.4mpg on a fast 3 tank highway trip last summer, but am now *always* on the gas as I enjoy a nice running H4 motor. My worst ever mpg with the K&N and purposefully spinning all 4 Blizzaks was 20.9. I'll see how it does when I get my RE92's replaced later this week. ...can't wait... :-) I may install a Cobb Tuning intake and put the K&N in my wife's Legacy SE, and see if she notices! Terry - '02 Regatta-Red 5spd Legacy GT wagon, 29,000 miles, Yakima / TandeMover / Rockymount rack. '03 Silver Legacy SE auto-sedan - 6150 miles. '85 CH250 - 4060miles! To reply, get rid of the "nonsense"

I installed it at 24K km. Just after 50K km I decided to get rid of it after long fight with my *ex*service shop re. engine ping.

Voja

TG wrote:

I'm not all that convinced they keep out dust as well as an oiled paper filter (like OEM Subaru). I once bought a drop-in K&N and a recharging kit. You can see through the mesh. The oil allegedly attracts dust by static attraction. They claim small cotton fibers are in the mesh holes, and that you have to really be careful cleaning and drying the filter when recharging it. The main thing I noticed about the K&N was that the air box did get louder. Even my dad could tell.

I've heard of people using K&N filters, who stopped after oil analysis showed excessive oil contamination. I've also saw an auto magazine test of a K&N cone filter. It definitely improved top end power, but it actually decreased power around 2K RPM.

That's about what my experience is with mine in my truck. Much louder intake, better top end, same or worse low end. Maybe more dirt int he oil but I never had it analyzed, there was never any dirt in the downstream side of the air intake. There were server trips on long dusty trails for hours behind another 4x4 where paper filters would have been clogging in no time, like the AC vents and even my CD player were. As it was I had to clean the K&N a couple of times in the field. On regular roads I don't think I would go K&N again, when I finally do get my Subaru I'll probably stick with aftermarket paper filters.

Doesn't K&N have "sleeves" for certain off-road applications - i.e. cylindrical air filters? There are less restrictive foam filters that can be cleaned. I remember the air box in a Briggs & Stratton lawn mower engine with a foam insert meant to be soaked in motor oil.

I think the OEM Subaru air filter isn't bad. Like I said - it's oiled paper. I bought a few, and there's definitely an oily residue on the inside of the plastic bag it's in, as well as on the metal frame. It cost me more (mail-order) than the $7 the Fram equivalent would be at a discount store, but I don't trust Fram. I once cut myself on one when the sharp metal mesh punctured through the soft rubber frame.

I've said it before, but here it goes again.

Before you install that K&N, ask yourself which manufacturer specifies K&N filters for their cars from the factory? Recall that with many high-performance brands, Porsche, BMW M's, Vette's, etc., price is really no object as what they are after is power; so if a $50 air filter us power even a little with no deleterious effect, they'd specify it for competitive reasons.

The answer is...none.

Further, every now and then Car & Driver tests these things as a after-market part add-on for one of their test cars. I've been reading C&D since the 60's and they have NEVER found a performance benefit over a oem filter.

On the other hand, if you are just after more intake noise or the right to have a cool K&N sticker on your car and don't worry about silica and other crap getting in your engine, go for it.

End of discussion, no?

I don't know about "none". It's not exactly "factory", but several aftermarket "performance packages" that dealers can order have K&N (or similar) filters. These packages are approved by the manufacturer and won't void parts of the warranty. Of course I'd tend to believe that any negative consequences of using a K&N filter would show up long past the warranty period.

I wouldn't say so. I've seen independent tests showing maybe a 2-5% increase in power at the top end, but a small decrease at low RPM. Of course the benefits are generally more pronounced (the fancy word is synergy) if there is a full set of performance headers/exhaust/etc - at which point you've just screwed up your warranty.

The answer is, they have their own version of the same thing. When's the last time you bought a part at a dealership that didn't have the car manufacturers name on it?

I don't think _any_ manufacturer installs oiled-gauze air filters.

Perhapsnot out of the factory.

However- I do seem to remember Ford has some approved aftermaket tuning packages. The dealer orders the package (w/ manufacturer's options codes), the car is delivered from the tuner, and the end result is a fully factory-warranted car. Someof these tuning kits include K&N (or similar) air filters.

However - if they're any problem from the K&N filter, it's not going to show up in the first 50K miles.

Honda has oil/foam filters for just about everything.

The Honda filters are washable. Just about every manufacturer has a washable foam filter for high dust environments. I've been on trails that clogged a paper filter to the point of causing the engine to sputter in under 3 hours. Of course the guy in the lead didn't have any problems :)