do you mean that a Ranger and an Explorer with the same engine don't use the same oil filter? Are they different sizes (diameters)?
Just for grins, you might try cross-fitting them. The reason I say so is many manufacturers make two different sized filters for the same engine, depending on suspsnion and exhaust clearances. If they do cross fit, use the largest one that works for both vehicles and you can by a case of them!
Heard certain autos when fitted with some high performance filters are subject to being hydro locked. It takes a very small quantity of water to destroy an engine. Anybody heard of this happening.
Changed to Wix on 2000 Alero & had a new Fram for 97 Astro. Did not see any improvement in performance or fuel mileage with either.
Was always skeptical about the dirt passing through and the possibility of oil getting on the MAF sensor.
As the lubrication engineer stated on one post, he can always tell, when doing oil analysis, if a K&N filter is on the vehicle. But he did say that the K&N would stop bricks and birds.
Oh well! it was a $100.00 learning experience. And I have always been one to purchase stake oil.
But, some aircraft reciprocating engines use a similar filter. My 108 HP Lycoming filter looked just like a K&N. However there is not that much dust and dirt at 8500' agl, except when Mt. St Helens erupted. There was a NOTAM issued about the ash and checking the air filter at that time, even in central US.
from what i have heard can be caused by a very small amount of water-some older BMW's used to have the problem when running through large water puddles.
never knew (way back in the 60's) that I would take his "very cool" T-bird and/or my Mom's Buick Wildcat out in the country to drag race on a nice stretch of flat road. Golly-darn, we were bored and it was something to do. First thing we did was REMOVE the air cleaner before the competition. I admit three things. (1) I'd disown a kid of mine who would do such a foolish thing, (2) the car sounded faster, and (3)the benefits were mighty small.
sound only comes from a flipped air cleaner cover!
I actually had my dad convinced it gave better performance and economy (on our family car, a '78 Fairmont with a 140 hp 302 V-8). I threw out some line of junk I learned in physics class....
when it comes to filtration? I am not talking about horsepower or fuel economy, just filtration. And is the difference great enough to be noticeable either way?
I am very concerned with taking good care of my car's engine. Thanks.
I use it. I have never heard a claim that it filters better. Just open the box and look at it and you will be able to tell it won't filter BETTER. They claim it gives better mpg and power. That hasn't happened for me either. The only advantage I see is never having to buy another filter. I am concerned that the filtration might be worse. The verdict is still out but it may let more through. I am going to use oil analysis to find out.
or you just like oiling it more often than the box says. It says to reoil it ever 50 K miles. It also says that dirt builds up and increases filterability so you are making it worse by cleaning every oil change.
I have noticed a Si reading that is a little high in the oil. Some have said that it could be dirt (sand is Si). I will check it again in a later analysis. What evidence do you have zues that it is filtering better? The wire screen sure doesn't appear as if it would filter better than paper. The pressure drop across it is lower as I have read also. That is a good indication that it is not filtering as much.
While I was with Super Shops, K&N and Mr Gasket (the primary maker of air filter elements for all the Moroso, Holley and Edelbrock chrome air filter housings) did dyno tests in San Bernardino with Steve Schmidt, head guy at Erson Cams and Mallory Ignitions (both owned at the time by Super Shops).
His tests showed 3-5% filtration improvement, measured through an a/c filtration system. The flow (for power and economy) was consistently 10-15% above paper filters. While those numbers aren't staggering, the idea of never buying another $10-20 air filter element is very attractive and has kept me a K&N guy for a long time.
filtered better or at least as well as paper was that although the openings are bigger in the K&N, the oil is present and catches more of the material an ordinary filter would let through.
I do like the way the K&N let's the car breath. Would perhaps more frequent oil changes be in order, or perhaps a Mobil 1 oil filter as opposed to going back to a paper filter?
I know K&N says to clean the filter at 50k miles. That sounds like a lot of miles to me, would you recommend cleaning the filter more frequently, and if so, at what intervals?
I will say that many knowledgeable car people use K&Ns, just go to Stangnet. But like all this stuff, oil types, filters, synthetic vs. dino, there are many opinions.
I told my friend to get one and he took it to his mechanic to put it on and his mechanic told him he was making a big mistake. But some of the smartest car people I know have told me to use the K&N air filter. And for a while it was offered stock on the Ford Mustang Cobra, the greatest car ever made (see, more opinions!).
50K is not cool - that's the standard to maintain the warranty (1,000,000 miles). Everyone who I've talked to with K&N and who uses K&N products recommends cleaning and re-oiling at least every other oil change - I do it every 3-4K - every oil change.
The machanic may have a valid point, or is listening to the rumors circulating around Jiffy Lube. If you soak the filter by using too much oil, the extra oil gets sucked into the MAF sensor and can cause problems.
clean your K&N more frequently. That is obviously a big difference, cleaning every 3-4k versus every 50k. Maybe that is the problem with the K&N some people are having, they are not cleaning it frequently enough?
Our chief editor has a article about cleaning K&N's.
I don't happen to agree with Karl myself, but he's a motorhead and I'm not :-). K&N advertises "as much as" x% increased hp and acceleration and have in the past touted x% increased mpg for their replacement air filter. That covers a lot of ground, including zero gain (don't see that mpg claim off-hand on their website tonight).
I can get a nice clean paper filter for my van every 15,000 miles for $7 and avoid getting a carcinogenic substance on my hands or into the waste stream.
From what I've read, K&N type filters typically allow a bit more air in but at the expense of dirt. If anything happens under warranty, it's your loss, Magnuson-Moss notwithstanding. Some people (one guy?) have reported on the net that the (excess?) oil from the K&N filter destroyed his MAF sensor.
So my personal opinion is that these types of filters give you more air for very little hp gains at the expense of the longevity of your engine. There's always the "if they're so good, why aren't they OEM" argument too (maybe they are - vettes perhaps?).
Even though I'm frugal I think I'm still ahead dollar-wise at 77,777 miles by using paper replacements.
Remember also that I change my dead dino every 7,500 miles whether it needs it or not and my in-cabin air filter is a cut up furnace filter from Home Depot :-). And while it's torquey, it's still a minivan that I'm driving. Need I say it? YMMV!
If K&N filters so effectively, why have they introduced the filter wrap? This follows Amsoil's theory as they have always had a wrap along with their gauze filter to trap more particles and prevent them from entering. Course K&N always could say to use these under dusty conditions, but one has to wonder.
developed and used many filters, I can tell you that there are only 2 factors that effect filtration and flow and those are surface area and pore size. The media itself only serves to provide different pore size capabilities and chemical resistances. You can only get more flow from a larger pore size or larger surface area. K&N claims the filter has a larger surface area yet the don't quote how much surface area the filter actually has. The pore size of a piece of gauze would appear to be larger than a piece of paper.
They also say that it "straightens and smooths" the air flow stream thereby "increasing engine performance". If this actually happens, they are talking about changing it from a turbulent flow stream to a laminar one. This would actually reduce the mixing that happens with the fuel. Turbulence always helps mixing.
I am a little wary of the claims that are made and now I am concerned about the MAF filter. Can someone explain to me what the MAF filter is? I am going back to paper on the next oil change and do a oil analysis to compare the Si content.
You might want to read coonhound's post #457. Why would a lubrication engineer say that he "could always tell when a K&N filter was being used" when doing an oil analysis? You should always check it out yourself and don't believe all the hype. Don't take my word for it. I like to do my own tests and I am just sharing my experience and knowledge about filtration. If I had to make a recommendation right now though, I would not spend the money for it again.
product K&N offers that goes over their regular filter and further screens out contaminents? Sounds like something I will be getting if this is the case.
I like K&N as a company. They have been around a long time, and a lot of car enthusiast swear by their air filters.
I'll buy the idea that the addition of oil to the filter will offer some additional protection.
I have one on my car and I like the way the car breathes with the filter and I like the increased throttle response.
I think the filter is well made and air filters are the company's speciality. I'd guess after all these years they would know what they are doing. If there was a problem with the filtration, I think the car enthusiasts who use K&N would have caught on by now and stopped using their product. Or K&N would have modifed or improved their product.
I also find the the fact that Ford Motorsports and Chysler/Mopar sell K&N air filters as a compelling argument for the company. I believe I read somewhere that Ford even dyes their K&N's Ford blue instead of the regular red.
K&N is very clear that using their filter will not void the warranty. I choose to believe them. (Now if you are a dumbo and put enough oil on the filter to turn it into minature oil well, and then that oil leaks onto the throttle body, then that is not the manufacturers fault, so I can see them not covering that.)
Perhaps the oil tech said he can always tell a K&N when he does an oil analysis, but there are so many opinions on these type of things! I know some mechanics love K&N filters and others hate them. I would have to see proof of a K&N signature being present in the oil analysis to convince me of this. If you know a link I would love to see it.
It also seems your driving conditions would be a factor. If you travel back roads in the country, or do some off roading, or live in a dust bowl like western Oklahoma, then air filtration becomes more of a problem. I don't have that situation.
Finally, what this controvery has done is made me rethink the oil change interval thing and oil filters. I got on Stangnet, and most the guys there are using Mobil 1 synthetic and changing it every 3,000 miles. It may be overkill, but I think it is insurance. And also, I will probably go to the Mobil 1 filter, which I believe will filter finer particles out. So this is my plan to deal with the K&N filter queston rather than getting rid of the K&N.
Finally, K&N says on their website that there are all kinds of claims out there about superior air filtration by different companies. The key is "claims". K&N has a good name, a lot of supporters, an interesting product and I'll give 'em a chance.
I may get an oil analysis down the road just to confirm the K&N is working and, well, just for fun!
I'd apologize for the bandwidth hit, but I know you guys don't care!
here's something I've learned working for a lawfirm - if K&N's products were bad for cars, there would have been several class action lawsuits against them that would have bankrupted them. Many people use their products and as consumers, we'd complain if there was a problem.
Sorry for the lack of analytical data, but I've always PREFERRED THE COMMON SENSE APPROACH !!
Here is a little hard data from K&N's website, it seems to say K&N filters as good at filtration than the OEM paper filters if I am reading it correctly:
OEM cumulative efficiency: 99.29% OEM paper initial pass: 96.47%
Both K&N and the paper filters stop 99% of particles on a SAE initial dust test. The OEM standard is 96%. The test uses particles as low as the 0 - 5 micron range and goes up to 20 microns. (Note form a novice: that sounds pretty small to me!)
Now I am NOT an engineer and I DON'T know exactly how to INTERPET these figures. But they seem pretty close to me. If there is a cause for concern on the K&N I have not found it yet IMHO.
is throw them all out and do his own tests or comparison. That is what I am doing with this thing. I don't believe anything that commercials (websites, TV, newspaper or packaging) say. You should never be gullible to believe what the company that makes a product says about it. Third party recommendations were enough to get me to try it but not enough to keep me buying it if it doesn't appear to improve anything for me.
It is too easy for some slick lawyer to get a company off in a lawsuit or have it get thrown out. There are so many ways to word advertisements so as not to get into trouble. Test procedures can be set up to get the results you want. Statistics can be manipulated to say whatever you are trying to prove.
I'd never insist that you keep something or try something on my word alone, but you could at least be respectful of the real world research I've already done in 18 vehicles and actual lab testing.
I'm not advertising for K&N, but so many times here on Edmunds, and most recently quite often with you, bigorange, I get a slam through your "I don't believe you, you must be full of poop" attitude. Gets more than a little old.
Engineers are just that way by nature. We have to prove things. We just don't take people's word for things that affect our own pocketbook. If is someone I know well and has alot of knowledge about cars it would be different. You can say anything you want on here. Some people are actually mean enough to say things they know are wrong to throw people off track and they have anonymity. How do you think computer viruses originated. I didn't say you were like that but I don't know you.
How about if I tell you that you should go invest $36K into XYZ stock, would you do it?
is going to cost you $36,000. Can we be a little more real here, or do we have to analyze the "real vs fantasy factor" through a series of calculations??
cost you $36K but it is a $36K investment that I am protecting. The damage I could foresee it causing if it does let more dirt through though would be in the $1000's if you have to replace some major engine parts early.
Let's put it this way, you have spent close to a $1000 on filters if you have bought them for 18 cars. Even for just a $1000 (though its much more if you factor in potential damage from all those 18 cars), let's say that I suggest you put $1000 into XYZ Internet startup company (or Enron 2000). I say that I know its a good company because the owner is a friend of mine and he knows the business. Are you going to do it? Thousands of Enron employees believed what the CEO and chairman of the board were telling them enough to put their whole retirement savings in company stock.
Don't expect me to put money into ANYTHING because of any experience you have had. Also, if you would buy something just because of what the company says it will do, I have a mansion that I will sell you for a $1 million. It's address is 1200 Swamp Road, Everglades FL. Just send me a check and its yours. You don't have to go look it, its a great place with a great view (he says with a grin).
Many opinions on the internet have contributed to me buying my first K&N but I have seen no benefit from it so far except for not having to buy another filter. No power increase or mpg at all. If the oil analysis doesn't show that it has extra dirt when using this filter, I MAY buy another just because of not having to replace it.
I don't take any layman's advice. In fact, I never listen to a layman on anything.
But if I had a buddy who was an investment broker and I knew him and knew he was successful, I'd listen to him.
Also, if I had a buddy who had been racing cars in 4 different formats since he was 15 years old (that's 24 years now) and had experience with just about every aftermarket manufacturer at the SEMA show (as a regional manager, very maker out there courted us so we'd know more about their products, so we'd sell their products).
That same guy has been in the car business for 10 years, just earned a masters in engineering 9automotive design and function).
I'd give his advice a little more weight than the guy down at Autozone or Pep Boys, that's for sure.
listen to his advice. The key word there is buddy. I don't have any buddies like that. But even then it would only be for an initial and maybe even a 2nd evaluation. But after 2 evaluations that show nothing, what sense does it make to keep throwing money down that rat hole.
obyone has a good post. Amsoil says that their foam filter beats K&N. You better switch to it for your next 20 cars.
but even if the filter performed (filtered) the same, with no improvements in mileage and power, a K&N would still be more economical than paper filters, because you only buy it once. Also, if you trade a Honda Accord EX V6 for another one, you can swap your filter and keep going.
I can't see it as throwing money down a rat hole, by any means, even if there is no performance gain.
My paper element filters cost between $10 and $14, depending on where I would get them. The K&N for my car was only $24.
Now, I have a cold air induction system that came with a cheap paper filter (conical). Interestingly, it was the same element as one I had from another car and the K&N I had mounted right up!
Amsoil - I don't doubt Amsoil produces good products, but until some of my racer friends (and other engineers) prove that Amsoil is better than K&N, I won't switch.
oil analysis here. I am very interested in seeing your findings. If something shows up that did not occur with the OEM paper filters, then I would definitely give that some thought. Until then though, it is just speculation.
I will say the reason I like the K&N is because with my car there is a noticable difference in how it breathes and sounds. But if you are not seeing a difference there, then it seems like an OEM paper filter may be just as good for your application. But then we don't get to hear about the oil analysis! So stay with the K&N, at least till you get that done. When do you think you will have it completed?
before I will be ready to post the comparison. I am at 19K miles and the oil change with the K&N will be at 24K miles. That should be about April. Then I will change back to the paper for 7500 miles and that would be up in probably September or October. I will certainly post the comparison here at that point.
on an earlier post I asked about the filter covers for the K&N. I was doing some more research and just like he said they don't fit my car's type filter.
On Bob the Oil Guy's site, they make the point that proper studies on engine oil and especially oil filters will probably never be done because of costs and the difficultly of doing them right. I think for this reason there will always be controversy. But K&N has been around a long time and has a lot of supporters. Now the 5W-20 Motor Water is another issue. I can find no good to that stuff except fuel economy...
Comments
Just for grins, you might try cross-fitting them. The reason I say so is many manufacturers make two different sized filters for the same engine, depending on suspsnion and exhaust clearances. If they do cross fit, use the largest one that works for both vehicles and you can by a case of them!
Being hydrolocked usually results from actual submersion - nobody wants to admit they took they 4X4 into a 3 foot ditch, so they blame something else.
Was always skeptical about the dirt passing through and the possibility of oil getting on the MAF sensor.
As the lubrication engineer stated on one post, he can always tell, when doing oil analysis, if a K&N filter is on the vehicle. But he did say that the K&N would stop bricks and birds.
Oh well! it was a $100.00 learning experience. And I have always been one to purchase stake oil.
But, some aircraft reciprocating engines use a similar filter. My 108 HP Lycoming filter looked just like a K&N. However there is not that much dust and dirt at 8500' agl, except when Mt. St Helens erupted. There was a NOTAM issued about the ash and checking the air filter at that time, even in central US.
I admit three things. (1) I'd disown a kid of mine who would do such a foolish thing, (2) the car sounded faster, and (3)the benefits were mighty small.
Odie
I actually had my dad convinced it gave better performance and economy (on our family car, a '78 Fairmont with a 140 hp 302 V-8). I threw out some line of junk I learned in physics class....
I am very concerned with taking good care of my car's engine. Thanks.
K&N filters won't do a bit of good, in fact they may be harmful, if you don't read the directions and maintain the filter.
I've had K&Ns in every vehicle I've owned since 1984. Never a problem.
I have noticed a Si reading that is a little high in the oil. Some have said that it could be dirt (sand is Si). I will check it again in a later analysis. What evidence do you have zues that it is filtering better? The wire screen sure doesn't appear as if it would filter better than paper. The pressure drop across it is lower as I have read also. That is a good indication that it is not filtering as much.
His tests showed 3-5% filtration improvement, measured through an a/c filtration system. The flow (for power and economy) was consistently 10-15% above paper filters. While those numbers aren't staggering, the idea of never buying another $10-20 air filter element is very attractive and has kept me a K&N guy for a long time.
I do like the way the K&N let's the car breath. Would perhaps more frequent oil changes be in order, or perhaps a Mobil 1 oil filter as opposed to going back to a paper filter?
I will say that many knowledgeable car people use K&Ns, just go to Stangnet. But like all this stuff, oil types, filters, synthetic vs. dino, there are many opinions.
I told my friend to get one and he took it to his mechanic to put it on and his mechanic told him he was making a big mistake. But some of the smartest car people I know have told me to use the K&N air filter. And for a while it was offered stock on the Ford Mustang Cobra, the greatest car ever made (see, more opinions!).
50K is not cool - that's the standard to maintain the warranty (1,000,000 miles). Everyone who I've talked to with K&N and who uses K&N products recommends cleaning and re-oiling at least every other oil change - I do it every 3-4K - every oil change.
The machanic may have a valid point, or is listening to the rumors circulating around Jiffy Lube. If you soak the filter by using too much oil, the extra oil gets sucked into the MAF sensor and can cause problems.
I don't happen to agree with Karl myself, but he's a motorhead and I'm not :-). K&N advertises "as much as" x% increased hp and acceleration and have in the past touted x% increased mpg for their replacement air filter. That covers a lot of ground, including zero gain (don't see that mpg claim off-hand on their website tonight).
I can get a nice clean paper filter for my van every 15,000 miles for $7 and avoid getting a carcinogenic substance on my hands or into the waste stream.
From what I've read, K&N type filters typically allow a bit more air in but at the expense of dirt. If anything happens under warranty, it's your loss, Magnuson-Moss notwithstanding. Some people (one guy?) have reported on the net that the (excess?) oil from the K&N filter destroyed his MAF sensor.
So my personal opinion is that these types of filters give you more air for very little hp gains at the expense of the longevity of your engine. There's always the "if they're so good, why aren't they OEM" argument too (maybe they are - vettes perhaps?).
Even though I'm frugal I think I'm still ahead dollar-wise at 77,777 miles by using paper replacements.
Remember also that I change my dead dino every 7,500 miles whether it needs it or not and my in-cabin air filter is a cut up furnace filter from Home Depot :-). And while it's torquey, it's still a minivan that I'm driving. Need I say it? YMMV!
Steve, Host
http://www.knfilters.com/wraps.htm
They also say that it "straightens and smooths" the air flow stream thereby "increasing engine performance". If this actually happens, they are talking about changing it from a turbulent flow stream to a laminar one. This would actually reduce the mixing that happens with the fuel. Turbulence always helps mixing.
I am a little wary of the claims that are made and now I am concerned about the MAF filter. Can someone explain to me what the MAF filter is? I am going back to paper on the next oil change and do a oil analysis to compare the Si content.
I've seen them damaged when guys put a quart and a half of filter oil on their K&N.
There's no model for the screen, that I know of, that will fit a K&N for your car.
I'll buy the idea that the addition of oil to the filter will offer some additional protection.
I have one on my car and I like the way the car breathes with the filter and I like the increased throttle response.
I think the filter is well made and air filters are the company's speciality. I'd guess after all these years they would know what they are doing. If there was a problem with the filtration, I think the car enthusiasts who use K&N would have caught on by now and stopped using their product. Or K&N would have modifed or improved their product.
I also find the the fact that Ford Motorsports and Chysler/Mopar sell
K&N air filters as a compelling argument for the company. I believe I read somewhere that Ford even dyes their K&N's Ford blue instead of the regular red.
K&N is very clear that using their filter will not void the warranty. I choose to believe them. (Now if you are a dumbo and put enough oil on the filter to turn it into minature oil well, and then that oil leaks onto the throttle body, then that is not the manufacturers fault, so I can see them not covering that.)
Perhaps the oil tech said he can always tell a K&N when he does an oil analysis, but there are so many opinions on these type of things! I know some mechanics love K&N filters and others hate them. I would have to see proof of a K&N signature being present in the oil analysis to convince me of this. If you know a link I would love to see it.
It also seems your driving conditions would be a factor. If you travel back roads in the country, or do some off roading, or live in a dust bowl like western Oklahoma, then air filtration becomes more of a problem. I don't have that situation.
Finally, what this controvery has done is made me rethink the oil change interval thing and oil filters. I got on Stangnet, and most the guys there are using Mobil 1 synthetic and changing it every 3,000 miles. It may be overkill, but I think it is insurance. And also, I will probably go to the Mobil 1 filter, which I believe will filter finer particles out. So this is my plan to deal with the K&N filter queston rather than getting rid of the K&N.
Finally, K&N says on their website that there are all kinds of claims out there about superior air filtration by different companies. The key is "claims". K&N has a good name, a lot of supporters, an interesting product and I'll give 'em a chance.
I may get an oil analysis down the road just to confirm the K&N is working and, well, just for fun!
I'd apologize for the bandwidth hit, but I know you guys don't care!
Sorry for the lack of analytical data, but I've always PREFERRED THE COMMON SENSE APPROACH !!
Here is a little hard data from K&N's website, it seems to say K&N filters as good at filtration than the OEM paper filters if I am reading it correctly:
Dust capacity:305 grams
K&N cumulative efficiency: 99.05%
K&N initial pass: 97.11%
OEM cumulative efficiency: 99.29%
OEM paper initial pass: 96.47%
Both K&N and the paper filters stop 99% of particles on a SAE initial dust test. The OEM standard is 96%. The test uses particles as low as the 0 - 5 micron range and goes up to 20 microns. (Note form a novice: that sounds pretty small to me!)
Now I am NOT an engineer and I DON'T know exactly how to INTERPET these figures. But they seem pretty close to me. If there is a cause for concern on the K&N I have not found it yet IMHO.
99% works for me and has for nearly 20 years.
It is too easy for some slick lawyer to get a company off in a lawsuit or have it get thrown out. There are so many ways to word advertisements so as not to get into trouble. Test procedures can be set up to get the results you want. Statistics can be manipulated to say whatever you are trying to prove.
I'd never insist that you keep something or try something on my word alone, but you could at least be respectful of the real world research I've already done in 18 vehicles and actual lab testing.
I'm not advertising for K&N, but so many times here on Edmunds, and most recently quite often with you, bigorange, I get a slam through your "I don't believe you, you must be full of poop" attitude. Gets more than a little old.
How about if I tell you that you should go invest $36K into XYZ stock, would you do it?
You know I'm messing with you, right?
Let's put it this way, you have spent close to a $1000 on filters if you have bought them for 18 cars. Even for just a $1000 (though its much more if you factor in potential damage from all those 18 cars), let's say that I suggest you put $1000 into XYZ Internet startup company (or Enron 2000). I say that I know its a good company because the owner is a friend of mine and he knows the business. Are you going to do it? Thousands of Enron employees believed what the CEO and chairman of the board were telling them enough to put their whole retirement savings in company stock.
Don't expect me to put money into ANYTHING because of any experience you have had. Also, if you would buy something just because of what the company says it will do, I have a mansion that I will sell you for a $1 million. It's address is 1200 Swamp Road, Everglades FL. Just send me a check and its yours. You don't have to go look it, its a great place with a great view (he says with a grin).
Many opinions on the internet have contributed to me buying my first K&N but I have seen no benefit from it so far except for not having to buy another filter. No power increase or mpg at all. If the oil analysis doesn't show that it has extra dirt when using this filter, I MAY buy another just because of not having to replace it.
Most are between $20-40, and there were several I was able to use in more than one vehicle (trading for a like vehicle, swap in the paper filter).
I was estimating an average price of $50 for the filters anyway to come up with $900 total.
But if I had a buddy who was an investment broker and I knew him and knew he was successful, I'd listen to him.
Also, if I had a buddy who had been racing cars in 4 different formats since he was 15 years old (that's 24 years now) and had experience with just about every aftermarket manufacturer at the SEMA show (as a regional manager, very maker out there courted us so we'd know more about their products, so we'd sell their products).
That same guy has been in the car business for 10 years, just earned a masters in engineering 9automotive design and function).
I'd give his advice a little more weight than the guy down at Autozone or Pep Boys, that's for sure.
http://www.amsoil.com/products/bf.html
http://www.amsoil.com/products/ts.html
Course one must take the results with a grain of salt due to the fact that the best performance is realized by their product.
obyone has a good post. Amsoil says that their foam filter beats K&N. You better switch to it for your next 20 cars.
I can't see it as throwing money down a rat hole, by any means, even if there is no performance gain.
My paper element filters cost between $10 and $14, depending on where I would get them. The K&N for my car was only $24.
Now, I have a cold air induction system that came with a cheap paper filter (conical). Interestingly, it was the same element as one I had from another car and the K&N I had mounted right up!
Amsoil - I don't doubt Amsoil produces good products, but until some of my racer friends (and other engineers) prove that Amsoil is better than K&N, I won't switch.
I will say the reason I like the K&N is because with my car there is a noticable difference in how it breathes and sounds. But if you are not seeing a difference there, then it seems like an OEM paper filter may be just as good for your application. But then we don't get to hear about the oil analysis! So stay with the K&N, at least till you get that done. When do you think you will have it completed?
http://www.seansa4page.com/resource/air filter.html
On Bob the Oil Guy's site, they make the point that proper studies on engine oil and especially oil filters will probably never be done because of costs and the difficultly of doing them right. I think for this reason there will always be controversy. But K&N has been around a long time and has a lot of supporters. Now the 5W-20 Motor Water is another issue. I can find no good to that stuff except fuel economy...