This was posted on an Acura site (from a BBB complaint):
I can't believe K&N does not stand behind their products. It is hard to trust what they claimed and if it could do any better for our engines. This is found from BBB website:
KIM'S CATCH OF THE DAY
K & N FILTERS
HERE'S THE CATCH: Consumers buy air filters based upon the seller's claims of their superiority, with seemingly no drawbacks. When the filters fail, so do other parts of the consumer's car, the warranty, and the company's responses to its complaints. The company's unfulfilled claims remain overinflated.
K&N Engineering, located in Riverside, sells air filters through its website. On the website they describe their air filter's "unique characteristics" which they themselves developed 30 years ago in their desire to win motocross races: a filter that is "washable, reusable, and built to last for the life of an engine." "A Revolution in Air Filter Technology" they claim.
Other claims are that using the filter will NOT void your vehicle warranty, that they warrant the filter for 10 years or one million miles, that it's "engineered to last the life of your engine," that it's designed to "increase horsepower and acceleration" and more.
The filters are described as four to six sheets of cotton gauze layered between two sheets of aluminum wire mesh, pleated and oiled "to enhance its filtering capabilities and overall performance."
Over the years, we've received a complaint about K&N Filters from time to time, but only five altogether in the last three years. Nevertheless, we assign the company an "F" rating. Part of the reason for that rating may become clear from the complaint of Ken Anderson, which he filed with us late last December.
Anderson, who owns a 2002 Nissan Xterra, is a U.S. Army Sergeant First Class with 21 years of military service to his credit at this point and now forwardly deployed in Germany. According to his complaint, he replaced his air filter with one of K&N's, and approximately 100 miles later, his "service engine soon" light came on. He took the car to the dealer, where the trouble was diagnosed as a faulty oxygen sensor.
Anderson had the repairs made under his warranty, but the same problem recurred, caused, again, by a faulty oxygen sensor. This time the mechanics found that the K&N filter was the source of the problem, but this time Nissan declined to cover the repair costs because of the K&N filter that had been installed.
K&N, to whom Anderson first complained, was little help. Anderson reminded them that their answer, in their website's Q&As, to the question of whether use of K&N's filter would void the vehicle's factory warranty, was that it is against the law for a manufacturer to require use of a specific brand of air filter unless it provides a replacement air filter, free of charge, under the terms of the warranty. Yet his experience had been otherwise.
Another question was "Can an engine get too much airflow?" K&N?s answer was no; an engine can take in a fixed volume of air, depending on the engine's size. Yet Anderson had been told, at the time of his vehicle's most recent repairs, that the vehicle was receiving too much air, and because the computer was trying to compensate for the extra air by adding more fuel to the engine, the oxygen sensor set off the codes to service the engine. In response, K&N wanted Anderson to return the filter (at a cost of almost as much as that of the filter itself) so that they could evaluate it and decide whether to refund anything beyond the cost of the filter. Anderson was disinclined to pay further shipping costs in addition to those he had originally paid in order to get his $44. So far, then, he is out a total of $194, which includes the replacement air filter and the oxygen sensor repairs. It does not include Nissan's charges for diagnosing the problem.
K&N did not respond to the complaint Anderson filed with us. Nor did the company respond to that of a Nebraska consumer who incurred a $444 repair bill when oil from service of the filter migrated and damaged his car's fuel injectors. Despite this complainant?s having obtained a small claims court judgment, K&N's general counsel advised him to drop the claim or accept the cost of the filter only.
KIM'S ADVICE: DON'T GET CAUGHT
A few tips can help you avoid making a bad purchase and incurring a costly repair job:
It's very important to get a reliability report on the company before you do business. There's never a reason not to get a report, but it may be even more important in proportion to how attractive the offer is.
Using a credit card to pay for the purchase may help in the case of a product that fails soon after purchase.
Check your warranty carefully before you use parts other than the manufacturer's.
Don't accept all of what you see on a website at face value. In this case the Magnuson-Moss Warranty Act, to which the K&N website refers, does prohibit requiring a purchaser to buy an item from a particular company to use with the warranted product in order to be eligible for service under its warranty.
What K&N doesn't tell you is that a manufacturer is within its rights to specify that the warranty will not cover use of parts that are not equivalent in design or quality to its own parts. If you decide to use other parts, use caution unless you're expert at determining the quality of such parts.
Finally, your warranty may well exclude consequential damages which, as all K&N complainants learned, can result in repair costs that far exceed the cost of the part that caused the damage.