How does the K&N filter work?
Engines produce power by igniting a mixture of fuel and air. The air filter's job is to filter out particles of dirt while allowing a free flow of air so the engines can "breathe". A filter that is clogged with dirt will cause loss of power and fuel economy.
Most air filters use paper as their filter medium. Most cars require the filter to be checked or changed every 10,000 to 20,000 miles; when the filter is dirty it is thrown away and replaced.
How is K&N different?
K&N filters use an oiled cotton filter medium. K&N claims that not only do their filters allow freer airflow when clean, but they can absorb dirt without getting as restricted as paper filters. When the filter gets dirty, you don't throw it away; you clean and re-oil it. K&N estimates the cleaning interval to be about 50,000 miles (longer for less dusty areas). The filter is serviced with a K&N cleaning kit ($9 to $12 retail ) which is good for 5 to 10 uses. K&N says their filter will last the lifetime of the vehicle, and covers their filters with a 10 year/million-mile warranty.
Benefits of the K&N filter
Paper air filters cannot be recycled; you have to throw the whole thing away. The K&N filter itself lasts the life of the car, and the cleaning kit uses cardboard packaging and plastic bottles which can be recycled.
Cost savings depend on the application. I tested the K&N filter on our 1996 Honda Accord. Retail price for the K&N filter is about $43. (My test sample was provided free of charge by K&N.) Paper filters range from $19 to $31. Honda recommends a filter change at 15,000 miles, so for a do-it-yourselfer like me, the K&N filter and a cleaning kit will pay for itself after two changes, or about two years. For people who have their cars serviced by the dealership, installing a K&N can pay for itself in a single change.
Here's the reaility: I'm not nearly as careful as I should be about changing my cars' air filters. By the time I get around to it, the filter is usually clogged with dirt -- and that means it's costing me more at the gas pump. The K&N's longer service interval means that I can gleefully ignore it without such adverse effects.
Other issues with the K&N filter
Several readers have responded with concerns about the K&N's ability to effectively filter dirt out of the air compared to paper filters. After all, engine protection is the reason engines have an air filter to begin with. K&N insists that their filters are rigorously tested to meet OEM filtration standards.
Expert opinion: Not an issue
I discussed the issue with the owner of a reputable engine rebuilding shop. In his experience, the engines that suffered from premature wear were those in which the filters were routinely ignored. He didn't see any significant difference in wear in engines where the filters were routinely cleaned or changed, regardless of type. (He personally runs K&N filters in his own cars.)
Will the K&N increase engine power?
Many enthusiasts use K&N filters because their increased airflow boosts power, especially in certain applications. If you are replacing a clogged air filter, you will definitely see a difference. My wife Robin and I didn't see a significant power increase; that said, we weren't expecting one -- K&N sells a special intake kit for Accord owners like us who want more power. (We will be testing one in the near future.)
- Easy installation - same as a paper air filter
- One less maintenance task to worry about
- Environmental advantages - less waste produced
- Potential for better long-term fuel economy
- High initial purchase price
A useful purchase for most car owners -- even if the cost benefits arent huge, the benefit to the environment is significant.