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K&N Air Filter

Hello, I was very surprised to find out from an independent mechanic that K&N air filters can cause problems to a vehicle down the road. I have used these filters before and have never noticed any problems. I assumed using this type of filter was better for the vehicle. Point being, I was shocked to hear the mechanic tell me this and discourage the use of the filter! Opinions?

I don’t like them either. If you buy a quality air filter then you don’t need one that costs a lot of money. I know a lot of people swear by them and say they get better fuel economy. They don’t. I tried regular filters, K&N filters and no filter at all. Same gas mileage. Let the floodgates open now for all the pro-K&N types. If no air filter does not get any better fuel economy what does K&N have? Magic? I will say that they are a quality filter but their claims are bogus.

They might give a little more hp at wide open throttle. That’s it. No reason for better mpgs. And I have heard conflicting reports about oil from the filter affecting the MAF.

I,d guess that any gains in performance are placebo effect rather than real. The turbulance and restrictions within the intake manifold, intake ports, exhaust ports, and even the valves cannot be overcome by reducing by a tiny bit any restrictions presented by the intake ducting in a modern car, and I seriously doubt of the filter itself is capable of a better flow rate. And I doubt if the air hitting the chambers is really any cooler.

And yes, I too have heard of problems with the filter oil coating the mass airflow sensor. Allegedly it’s from overoiling, but since I don’t see the point of the K&N Filters to begin with, why risk it?

The only possible benefit is at wide-open throttle, when possibly a bit more air gets through. Any other claims are bogus.

There have been discussions here in the past about damage to the MAF sensor due to the oil.

The one thing I don’t like about it…is it doesn’t clean the air as well as the standard filter does…and since you car will consume 10,000 gallons of air for every 1 gallon of gas…I’d like to have the air as clean as possible…lot less chance of problems down the road.

I use them. I have a CAI setup on both my Bronco and my Mustang. The one on the Bronco has been on there for over 100k miles, I clean them properly every 30k-35k miles or so and have had zero issues. The problems you hear about them killing MAF sensors is mainly due to people not cleaning and reoiling them properly.

The bobistheoilguy site used to have a filtration test with results that were not complimentary to K&N filters. K&N may have threatened them as the results are now dumbed down. The old results did show K&N to be worse at particle filtration.

K&N may flow better at maximum throttle but you don’t care about that if normal driving is what you do and maximum engine life is your goal.

How long is it possible that people will remember this about K&N and Bobistheoilguy?

On a stock vehicle there’s no benefit, and the oil on the filter media can have adverse affects on downstream components.

The standard paper filter is the best thing for normal road use.

Look at it this way; if the K&N is so good, why isn’t it standard equipment? The factory engineers are always trying to maximize performance, economy, and reliability. If a K&N filter was better than a paper filter, they would specify its use.

You can expect a very slight (likely too small to measure) mileage increase, and maybe a small power increase at high RPM. You can also expect a damaged MAF unless you are very careful and good at oiling the filter.

It certainly is not worth it for me.

Note: they do make dry filters as well as oiled filters, but I believe you need to do some modifications to use one. Again it is not likely worth the gain expect for comerical race cars.

They are actually standard on some cars, they came stock on the Dodge Viper with the ACR package, They are standard on the Shebly Mustang GT500KR, and are standard with various Roush/Saleen Mustangs as well. They arent standard on more ordinary cars because they cost 3 or 4 times as much as a standard paper filter, and most people don’t know how to properly clean/reoil them. They don’t filter air as effectively as a paper filter, but they filter well enough to the point where your car will expire from other causes rather than failing because the filter let too much dirt through.

On a N/A car though, the power gains are minimal, but K&N’s really shine on cars with forced induction. My car picked up 5 RWHP going from a paper filter to a K&N. Though I will admit that paper filter I used had around 3,000 miles on it, and the K&N was right out of the box.

I think the biggest problem with these kind of filters are that people do not know how to service them correctly. I’ve had one on my truck for over a hundred thousand miles with no adverse effect and even use them on my diesel engines on my boat. You should see the amount of soot these filter collect. I for one swear by them and so are a lot of my car buff friends.

When a paper filter is neglected it stops flowing well and the owner has to change it. When an oilable filter is neglected, it stops filtering but the car keeps running fine despite possible internal damage being done.

Now, consider how much interest the average car owner is going to take in inspecting their air filter, and how many partially plugged paper filters that are driving around at this very moment. Thats the big reason why oilable filters don’t come on cars any more!

But, I agree that just dropping in a marginally higher flow filter ain’t gonna do squat on an otherwise unmodified car.

I’ve read a lot of replies from some readers who probably never even used one. My 2007 F150 went from 15.7 MPG to 16.8 MPG after I installed a K&N air pak. I have the digital readout to tell the mileage. It also cleaned up the engine compartment and sounds great when kicking into passing gear. I’ve used them for many years on all my vehicles with no problems.

The instrumented tests I’ve read showed zero impact on milage. I can think of no reason the filter would affect milage, as long as it’s not plugged up. The throttle plate controls the pressure drop in the intake, not the filter.

Been using them for 2 decades in a Supra, Cressida, Camry, 2 Oldsmobiles, 2 Chevy Malibus, Mazda B truck (Ford Ranger Incognito) with ZERO problems. Great throttle response and very good gas mileage. Also makes exhaust sound more throaty when I tromp the accelerator, which is great. Most dramatic mile per gal increrase was with the B Truck. I clean the K&Ns with orange grease cutting cleaner and hot water (in the kitchen sink) - takes about 5 minutes - and never re-oil the filters. No problems whatsoever with any vehicle. Friends who use K&N air filters like them and report no problems, either. And, how can you beat one filter for 1 million miles!

The only way for an aftermarket filter to admit more air into the same engine that is operating under the same conditions is by making it more porous; as in allowing particles of a larger diameter (in microns) through. Living here in dusty OK that’s the last thing I would consider doing.

Placebo more than anything else in my opinion.

I was curious and installed the K&N in a Cherokee many years ago. If there were any performance or mileage improvements they were negligible. In the long run it saved money by being easily cleaned and re-installed. The Cherokee was junked at 300,000+ miles with the engine still running well. There was no MAF senser on the Cherokee and it is understandable that over oiling the K&N might cause an expensive problem there. But poor maintenance of a paper filter will often result in trash and engine blow-by damageing the MAF. Fastidious owners will likely have no problem whichever filter they choose.