No noticeable increase in MPG or HP

Caused check-engine light to come on

After 10,000 miles w/K&N air filter, engine light came on, Air Flow sensor had oil on it causing light to come on, technician noticed K&N label and determined the oil from the filter caused the problem, instead of going thru this again, I changed to normal paper filter.

62 YEAR, OLD MALE USED ON THE FOLLOWING CARS, MONTE CARLO,2 DAKOTAS, 1 RT, DODGE MAGNUM, CADILAC DEVILLE. HYUNDAI SONATA, SUZUKI SX4, HYUNADI VELOSTER ALL SHOWED MARKED IMPROVEMENT GAS MPG AND ACCELERATION.OVERALL IMPROVEMENT PERIOD.

NONE

GET ONE, BEEN USING FOR 30YRS. NEVER ENCOUNTERED ANY OF THESE ALLEGED PROBLEMS.IF THESE WERE MESSING UP ENGINES THEN WHY SUCH MASSIVE USE BY COMMON FOLKS AND RACERS TOO. I'D PUT ONE IN MY LAWN TRACTOR IF IT WAS MADE. PS. ALSO HAD ONE ON MY HD SPORTSTER

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DIDN'T NEED TO

dont have to change it every 6 mos

none at all

having a niche vehicle--no one was making an aftermarket air filter---the stock dealer price was 40+ after tax---so I decided to add 10 bucks,no tax- free shipping,and try K&N---noticed about a 10 % increase in torque and go---prob an extra 4 hp---plus dont have to change it for quite a while--4 me --its worth it--- a 4 star product

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stock only

Better flow means more air

Better flow also means less filtration. Also messy work of cleanning with special detergent and oil (costly too!)

Get better MPG, better response but very dirty intake. The filtration rating is really up to the amount of oil coating, more oil better filtration, but less flow.

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Hurricane SS filter, High Performance fabric filters and SS filters.

improved fuel economy

reduced low end torque

no performance increase
but did notice some improvement on MPG

engine rev more at 2nd and 3rd gear

Better Miles per Gallon
Better RPM running rate (lower - better on the engine)
Re-usable, environmentally friendly

Initial cost is the only "weakness" however once you realize the benefits you are receiving, that is an insignificant point.

I have just installed a K&N Filter on my new Impala (with a 3.5ltr V6) and it helped significantly. I have had these filters on all of my cars since the very first one I have purchased and they are amazing. I have had recommendations from many mechanics and auto enthusiasts and everyone seems to agree that K&N did very well with the filters. I have noticed an increase in the MPG (better!) and the RPMs (lower!) and it helps your vehicle shift better.

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Factory, OEM, stock paper filters

Better performance, milage and a better sound from the engine.

None

I had put one in my 2004 Accord V6 and was impressed with gain in performance, so when I bought the Civic I bought another one. The stock air filter was 3 inches thick the K&N is .5 inches thick.

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paper filter

Smooth durning at an speed

none

Since Mazda wanted $22 for the stock Filter, I thought Why not just try the K and N. filter was simple to replace. I'm not sure if it will increase performance or fuel but did notice a smooth responce through all the gear...

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Stock filter

Work as advertised in most vehicles. Well made.

Expensive. Require some user maintenance, which may be beyond some users. Low restriction means less effective filtering than a paper filter so don't use them on your off-road vehicle of if you frequently drive on non-paved roads.

Used a K&N on my Nissan AND a 2006 Chrysler Town & Country and had better power and highway fuel economy. There was nothing earth shattering about the power improvements - just a bit more pickup - but the highway economy was a definite improvement. I saw a 2 MPG increase with the Chrysler and a 3.5 MPG increase with the Nissan (This is with a combined average mileage of almost 20,000 miles) but no noticible differences in stop-and-go MPG with either car. Mostly freeway driving and never off-road so I have not had a dust problem.

These work as advertised and seem to be adequate as far as filtration goes. Both the airboxes are sparkling clean.
I have never seen oil leaking or misting away from a K&N unless it was over oiled. REMEMBER - these are pre-oiled and do not need reoiling unless they are first cleaned using the prescribed cleaner. I suspect that most who had MAF damage have either oiled a non-cleaned filter or used too much oil when reoiling. These things come with an instruction sheet that should be followed. If you mess up your car because you can't follow instructions then it is your fault and not K&N's or the car mfg's.

The local Nissan dealer puts K&Ns into their performance vehicles - both the cold air kit and the air filters. Nissan sez to unhook the battery for at least 5 minutes so the computer will reset after you put the new filter in (or go back to the stock filter). Don't do it and the car won't run right.

With the Chrysler it was a simple drop-in. The service manager at the local dealership uses K&N and has for years. He sez he has never had a problem with one that was properly used. Of course, the local Mercury service manager sez not to use them so I don't in my Merc.

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Fram and Purolator stock filters

Let more air, and more dirt, in than stock.

Throw off the air/fuel mixture balance. Wear out the engine faster than stock, paper filter.

I've used k&n air filters in 2 cars and 1 motorcycle over the last 7 years. There's one thing I can say from experience. They wear out the engine faster than a paper filter. Yes, they let in a little more air. They made the motorcycle slower and didn't improve either of the cars I put them in. Overall, I can't recommend them under any circumstances. Sorry, but that's been my experience.

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Stock, paper filters.