Pros: low cost maintenace, Never needs replaced, long lasting performance before cleaning is needed.
Cons: Initial price, no horsepower gains or MPG gains.
A couple of years ago I purchased a K&N "drop-in" type filter (#33-2192) for my Honda Civic with hopes that I would get a boost in MPG and maybe even a small boost in horsepower. The K&N Company makes all sorts of outrageous claims about how their air filters increase horsepower and MPG, so I thought I would cough up the 50 bucks for one of these supposedly superior air filters. Did the K&N filter live up to its claims...? Or was I scammed into thinking I could actually get better MPG and horsepower by using just a fancy air filter?
What is a K&N Filter?
A K&N drop-in filter replaces your vehicle's conventional paper or foam filter; there is no need for any modifications or tools, just take out your old air filter and place in the K&N filter. K&N makes air filters for virtually every make and model of vehicle: even classic cars and ATV's, so it's likely you will be able to find a K&N filter for your specific vehicle.
The way a K&N filter works is fairly simple. The K&N air filter is made of multiple layers of oiled cotton gauze sandwiched between an alloy mesh screen. This oiled cotton gauze traps dirt like a conventional air filter, however unlike your run of the mill paper or foam filter a K&N filter can be reused over and over again by cleaning and re-oiling; the K&N Company claims that owners can go up to 50,000 -100,000 miles between cleaning (depending on your driving conditions).
According to K&N, the multiple layers of oiled cotton gauze of their filters increase airflow into the engine, thus allowing fuel to be burned more efficiently. The result? Supposedly, increased MPG and increased horsepower.
Ease of installation:
As mentioned, this filter simply replaces your vehicle's existing air filter. So, depending on your vehicle (in this particular case a 2004 Civic), it is completely painless to install, taking less than 2 minutes in most cases.
Ease of cleaning:
Cleaning your K&N filter is very easy, although it is time consuming. In order to clean your filter you must first purchase the K&N filter recharge kit that contains specialized cleaner and oil (one cleaning kit will cost about $12 and will clean approximately 4 filters). You will have to soak the filter in the K&N cleaner for about 10 minutes, rinse, let dry, and then re-oil the filter. The process sounds pretty simple and it is, but it does take time. That said, you most likely will need to have a spare air filter on hand to use in your vehicle while you are cleaning your K&N air filter, as it can take up to 2 days for the K&N filter to completely dry: something that is 100% necessary before reinstalling the K&N filter back into your vehicle.
Having my K&N filter installed for well over 40,000 miles, I have not noticed any significant increase in MPG over the old paper-type Fram filter that was previously installed in my vehicle. With just the cheap paper Fram filter I was getting about 30 MPG in the city and 40 MPG on the highway with the cruise control set at 70 MPH in my Civic; with the K&N I have consistently received the same 30 city/40 MPG on the highway. While I am disappointed to report that I didn't gain MPG using this filter, I am surprised how long this filter allows me to achieve good gas mileage. To explain, after 30,000 miles of use with the K&N (no washing) I'll still get excellent gas mileage. With a paper Fram or Denso filter, however, my gas mileage starts to degrade significantly after just 12,000 or so miles.
While I have experienced modest power gains using K&N's short ram intake systems, the drop-in variety hasn't done much for my Civic in terms of power. I did notice a slight improvement in throttle response, but not much else: I certainly didn't notice any dramatic increase in power at any particular point in my Civics' powerband. With this being the case, if you are under the impression that you will get a bunch of horsepower from a K&N drop-in filter, you'll likely be disappointed.
So, I didn't gain any horsepower or MPG from my K&N filter, however I have noticed a smoother running engine. After using the K&N filter my engine seems to idle smoother, it starts up easier, and as mentioned throttle response seems to be a tad bit better than it was when just a regular paper filter was being used.
Is a K&N filter bad for your engine?
Because a K&N filter allows more air to flow into your engine than a paper or foam filter, many may be concerned about impurities that may also pass through the filter media, thus clogging up the throttle body or the MAF sensor. I recently had my throttle body cleaned and it looked about as dirty as it would with any other filter. Also, I have had no problems with the MAF sensor or any other intake components.
Does it void your car's warranty? No.
How long will it last? At 40,000 + miles mine still looks like new and I don't foresee having any problems in the near future. According to K&N, their drop in filters will last up to 1,000,000 miles (the life of your vehicle) and K&N provides a warranty for that period.
Does the K&N filter work just as good after you wash and re-oil it? Surprisingly yes! I was almost sure that after washing this filter it would never work as good as it did when it was new. However, after washing and re-oiling my K&N filter I received the same performance as I did when I first installed it.
Price and Warranty:
The price for this particular model of K&N filter (for a 2001-2005 Civic EX) costs between 39.99 at some discount online stores to 49.99 at auto parts stores like Kragens, Autozone, or Napa. The prices for K&N drop-in filters vary slightly for every vehicle however, but most run between $40 and $50, so it's a fairly affordable filter: especially when taking into consideration that it never needs to be replaced. As mentioned, K&N provides a 1 million mile warranty, so if you notice any tears in the filter media or find that it's not filtering as well as it should, K&N will exchange it for another filter free of charge.
I really like this air filter. While it didn't make my Civic a racecar nor did I see noticeable gains in MPG, my engine does seem to run smoother with a K&N versus a cheap Fram or DENSO filter, plus it never needs to be replaced. If you are on the market for an air filter for your vehicle I do recommend a K&N drop-in filter, just don't except any performance or MPG gains. If increased performance is what you want, going with a K&N cold air intake system or K&N short ram intake system will most likely be your best bet. I have since upgraded to a K&N Typhoon short ram intake and have experienced noticeable gains in power, albeit modest and a slight increase in MPG.
Thanks for reading!