To Use A K&N Filter or Not

[Steve K (IA)]

Going to change the vacuum lines on my I/S.  Into it's 16th season, guess it's time.  The way it has started running makes me sure I have a vac leak.

Anyway, I have a new K&N filter on the shelf I've had for a few years that was part of a trade.  Wondering...if the air filter looks like it needs replaced,  should put it in or get an OEM filter.

I did a search on this and someone suggested that the K&N doesn't filter quite as well as stock.  IF I use the K&N, do I use the prefilter I've hear about and believe it's in the box?  (I've never opened it)  Only thing not stock is my Mark T exhaust.

Thoughts, suggestions?

[Paladin528]

There shouldnt be an issue using it.  I have run K&N filters in all my vehicles with no issues.  Some will say you need to rejet but that shouldn't be necessary if all is ok now.

[F6Dave]

This has been discussed at length here, so last year ago I did some fact finding on the web.  Here's a post summarizing what I learned:

I've used both K&N and another 'serviceable' oiled air filter in the past, on bikes I rode for nearly 100K combined miles.  So I've had several opportunities to clean, dry, and re-oil these things.  That process is a pain.  It's so much easier to just drop in a new replacement filter.  And if that's not enough, a K&N isn't cheap.  I've never paid more than $20 for an OEM filter for my Valkyrie or GL1800.  A K&N will cost about 3X that much, or 4X if you include the cleaning/oiling kit.  At that price you need to ride years just to break even.

The high price of a K&N might be acceptable if they worked as well as paper filters, but they don't.  Over time I've seen informal tests indicating they don't filter well, but those tests were somewhat basic and short on specifics.  Then I recently found results of a comprehensive ISO 5011 test that compared a K&N with 8 other air filters of the same size.  This test uses a high tech (and high $$) machine to flow air and test dust (with a specific distribution of particle sizes) at a precise rate.  After testing, dirt captured by the filter is weighed, as is dirt that passed through the filter, to calculate filter efficiency.  The test also determines how quickly a filter clogs up, by measuring how long it can flow a constant mix of air and dust before air restriction causes a pressure drop of 10 IN-H2O greater than the initial restriction.

The results of this test are posted in multiple internet locations.  I found it on a Nissan/Infinity Car Owner (nicoclub.com) discussion board, though other sites include more detailed tabular data.  You can read it (search:  K&N air filter test results) if you're interested in the details.  I'll just summarize in terms of efficiency and capacity, which is what matters to me.

As far as efficiency, the best filter tested was an AC-Delco, at 99.93%.  The K&N was the least efficient, capturing only 96.8% of the test dust.  The paper element filters were consistently much more efficient than the serviceable (foam and fabric) filters, so this is useful data even though the tested filters were not sized for our bikes.

I already knew the K&N was less efficient, so that result was no surprise.  But I didn't expect the paper filters to have such higher dirt retention capacity.  I had believed the claim that oiled filters had longer service intervals, which apparently is a myth.  Here the AC-Delco was again the best, running for 60 hours before plugging up, and capturing 574 grams of dirt while passing only 0.4 grams.  The K&N plugged up in 24 hours (next to last of the 9 tested) and captured 212 grams of dirt while passing 7.  The author didn't mention why paper filters had such a greater capacity, though I suspect the tightly packed corrugated paper allows more total surface area (and more pores to clog) than the thicker fabric media.

To be fair, the author pointed out situations where foam or fabric filters make sense, such as off-road vehicles where water or mud can cause paper filters to collapse, or competition engines where high airflow is more important than high filtration efficient.

In the real world a lower efficiency filter may not make a difference.  GL1500 and GL1800 engines can last hundreds of thousands of miles with minimal maintenance.  Since the vast majority of owners never come close to wearing these motors out, some extra dirt may only show up as higher silica contamination in an oil analysis, and barely measurable wear on internal parts.  With this in mind, when I bought my F6B I seriously considered trying a K&N again.  Since a Goldwing filter change is so difficult, a longer service interval would be attractive even at the expense of more dirt in the engine.  But if an oiled filter like K&N traps less dirt, and also clogs up faster than a paper filter, it's hard to justify the cost or effort .  I'll stick with the OEM Honda filters.

[Steve K (IA)]

This has been discussed at length here, so last year ago I did some fact finding on the web.  Here's a post summarizing what I learned:

I've used both K&N and another 'serviceable' oiled air filter in the past, on bikes I rode for nearly 100K combined miles.  So I've had several opportunities to clean, dry, and re-oil these things.  That process is a pain.  It's so much easier to just drop in a new replacement filter.  And if that's not enough, a K&N isn't cheap.  I've never paid more than $20 for an OEM filter for my Valkyrie or GL1800.  A K&N will cost about 3X that much, or 4X if you include the cleaning/oiling kit.  At that price you need to ride years just to break even.

The high price of a K&N might be acceptable if they worked as well as paper filters, but they don't.  Over time I've seen informal tests indicating they don't filter well, but those tests were somewhat basic and short on specifics.  Then I recently found results of a comprehensive ISO 5011 test that compared a K&N with 8 other air filters of the same size.  This test uses a high tech (and high $$) machine to flow air and test dust (with a specific distribution of particle sizes) at a precise rate.  After testing, dirt captured by the filter is weighed, as is dirt that passed through the filter, to calculate filter efficiency.  The test also determines how quickly a filter clogs up, by measuring how long it can flow a constant mix of air and dust before air restriction causes a pressure drop of 10 IN-H2O greater than the initial restriction.

The results of this test are posted in multiple internet locations.  I found it on a Nissan/Infinity Car Owner (nicoclub.com) discussion board, though other sites include more detailed tabular data.  You can read it (search:  K&N air filter test results) if you're interested in the details.  I'll just summarize in terms of efficiency and capacity, which is what matters to me.

As far as efficiency, the best filter tested was an AC-Delco, at 99.93%.  The K&N was the least efficient, capturing only 96.8% of the test dust.  The paper element filters were consistently much more efficient than the serviceable (foam and fabric) filters, so this is useful data even though the tested filters were not sized for our bikes.

I already knew the K&N was less efficient, so that result was no surprise.  But I didn't expect the paper filters to have such higher dirt retention capacity.  I had believed the claim that oiled filters had longer service intervals, which apparently is a myth.  Here the AC-Delco was again the best, running for 60 hours before plugging up, and capturing 574 grams of dirt while passing only 0.4 grams.  The K&N plugged up in 24 hours (next to last of the 9 tested) and captured 212 grams of dirt while passing 7.  The author didn't mention why paper filters had such a greater capacity, though I suspect the tightly packed corrugated paper allows more total surface area (and more pores to clog) than the thicker fabric media.

To be fair, the author pointed out situations where foam or fabric filters make sense, such as off-road vehicles where water or mud can cause paper filters to collapse, or competition engines where high airflow is more important than high filtration efficient.

In the real world a lower efficiency filter may not make a difference.  GL1500 and GL1800 engines can last hundreds of thousands of miles with minimal maintenance.  Since the vast majority of owners never come close to wearing these motors out, some extra dirt may only show up as higher silica contamination in an oil analysis, and barely measurable wear on internal parts.  With this in mind, when I bought my F6B I seriously considered trying a K&N again.  Since a Goldwing filter change is so difficult, a longer service interval would be attractive even at the expense of more dirt in the engine.  But if an oiled filter like K&N traps less dirt, and also clogs up faster than a paper filter, it's hard to justify the cost or effort .  I'll stick with the OEM Honda filters.

Thanks for that information.  I may just hang onto the K&N and use for a trade further on down the road. 

[Willow]

I run K&N on my Standard.  It has 190,000 miles on it.  If K&N doesn't filter as well as OEM then apparently it takes a long time to make a difference.

Oh, I also get better fuel mileage than most and I do run without the prefilter.

[Steve K (IA)]

I run K&N on my Standard.  It has 190,000 miles on it.  If K&N doesn't filter as well as OEM then apparently it takes a long time to make a difference.

Oh, I also get better fuel mileage than most and I do run without the prefilter.

Ok, well, hmmm.........the test results show a very minimal difference in filtration between OEM and K&N.  I just may put it into service after all.  One positive, I don't need to go out and spend $20 on a new filter.

I get 40 mpg when riding conservative.  Would be a plus if that number increases.   

 

[Jess from VA]

They both work OK.

The K & N application chart calls for the prefilter to be used on a Valkyrie.  Probably OK without it, but once 12-18 months goes by and the K & N oil is bone dry, wouldn't you feel better with the prefilter?  I used it in mine, and when removed, most of the crud was on the prefilter and not the filter itself.

Since I am essentially lazy about yanking the tank just for a filter, I tend to let mine go long (and my filters have never been really filthy; all the dirt is on the back side two inches around the intake), so I prefer the OE to the K & N, on the theory that at 12-18 months there is no wet oil left on the K & N, but the OE is still going strong.  

I have a perfectly serviceable cleaned and oiled K & N ready to go, and I should change them in both my bikes this fall.  I have to order one, so I will probably order two.

The other variable is how dusty is your riding area?  Mine is not very dusty.    

[Steve K (IA)]

Not very dusty where I am at. 

Taking the tank off is my least favorite thing to do to these machines. 

Been sitting here reading past threads.  Getting more confused the more I read.  Since I will have the tank off and airbox out, I will change the air filter while I'm in there no matter what the current one looks like.

[98valk]

the Spicer air filter test

http://www.billswebspace.com/AirFilterTest.htm

a k&n always lets dirt in. there is always dirt in the air.
 these fine particles are scratching the cylinder walls reducing compression by increasing blow-by. some say u know the bike just doesn't run like it did when new and some engines it is so slight over the yrs one gets accustom to it and doesn't even realize the loss in HP and MPG.
  any Technician doing a used oil analysis, will know immediately if a k&n is being used, there will ALWAYS been dirt, silica, etc in the oil sample. The oem is a highly efficient filter flows more than enough air, it supports over 100 hp in dyno runs. it is not paper but a synthetic fiber type. there are some sport bike dynos posted that show a k&n actually lost HP on the top end over the oem filter.
the filter will last much, much longer than 12k. when your mpg, performance and your plugs are getting carboned up then its time to replace the filter. 12k change out is Honda's protection for worst case like one lives in the country and  rides on dirt roads more than non-dirt.
years ago I actually did an airflow test with a spare air box I have using a CFM airflow meter. I found no difference btwn a brand new oem and one with 15+k miles on it.

[F6Dave]

Here's a thought.  Manufacturers of cars, trucks, and motorcycles are spending BILLIONS to achieve very small improvements in fuel economy.  Look how much Ford spent on aluminum bodies for the F150 just to shave off some weight.  If they could pick up some mileage by simply increasing airflow, either with a larger airbox or more porous (like K&N) filter, do you think they would?  Absolutely!

I've read that Honda engineers motorcycle intake systems as well as anyone.  The GL motors are low revving, with moderate airflow needs.  Yet the airboxes and filters on my Valks and Wing are nearly as large as that on my car.  I have no doubt the OEM filter flows all the air the engine is able to handle.

[98valk]

Here's a thought.  Manufacturers of cars, trucks, and motorcycles are spending BILLIONS to achieve very small improvements in fuel economy.  Look how much Ford spent on aluminum bodies for the F150 just to shave off some weight.  If they could pick up some mileage by simply increasing airflow, either with a larger airbox or more porous (like K&N) filter, do you think they would?  Absolutely!

I've read that Honda engineers motorcycle intake systems as well as anyone.  The GL motors are low revving, with moderate airflow needs.  Yet the airboxes and filters on my Valks and Wing are nearly as large as that on my car.  I have no doubt the OEM filter flows all the air the engine is able to handle.

Exactly. 
In fact one of the first airflow more HP test results K&N published way back in the beginning was a Chevy. I tend to remember it was either a 4 or 6 cyl that happened to have an undersized air box for max power. so putting their high flow filter in would show more power. They were slick and still are.
their filter is a race track/off road item should never be used on the street if one wants cleaner, longer oil changes and max efficiency of the engine for 500+k miles.
not convinced read up on Ford, Dodge and Chevy diesel truck owners who were using K&N filters and types like, who found out their turbo's  got wiped out from all of the dirt getting by the filter.