K&N Air filter- Good or Bad?

[97JInCO]

I am new to this forum and am hoping for some opinions. I recently installed a K&N filter in my J hoping that I would gain a few MPG's, but the mileage has actually gone down. I have a K&N in my turbo Z and also had one in an Expedition and had good luck with both applications. The only difference is the exhaust systems; high flow systems in both my Z and the Expe, and a stock system in the J. What do y'all think, should I knock the cats out of my J? Any advice would be appreciated!

[Victor]

I bought my J30T used and it came with a K&N conical air filter. I took it off and replaced it with the original air filter and air filter box and my car seemed more powerful with the original. Also, I didn't want to mess with cleaning an air filter. I read reports that oiled filters like the K&N let in much more dust into your engine than the regular paper filter. Also, the original filter already gives you more than enough air flow for an unmodified engine. Plus the K&N gets it air from inside the engine compartment instead of cold air from outside, which would marginally make your engine less efficient with the K&N.

[kbflip02]

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I am new to this forum and am hoping for some opinions. I recently installed a K&N filter in my J hoping that I would gain a few MPG's, but the mileage has actually gone down. I have a K&N in my turbo Z and also had one in an Expedition and had good luck with both applications. The only difference is the exhaust systems; high flow systems in both my Z and the Expe, and a stock system in the J. What do y'all think, should I knock the cats out of my J? Any advice would be appreciated!

i had excellent luck w/ my srop in K&N filter....however when i switched to the JWT pop charger it did slightly worsen...then while i was doing the cams,injectors,pulleys,ETC i modified it to be a true cold air intake using pvc fitibgs and dryer duct....works great now

[Jakw]

From what I've seen, the K&N actually does a worse job of filtering than a stock-style filter. I personally choose engine longevity over what, like 3hp (if any)?

[97JInCO]

Thanks guys for your input on this. I too prefer engine longevity over 3 hp, if any. I did not install a K&N for performance as I realize that the J30 is not a rocket ship, but rather a luxury sedan. If I want to go fast, I'll pull my Z out of the garage and eat a few WRX's and Honda noise makers. Also, I don't think anyone running a K&N in the middle of metropolis will notice a drastic decrease in longevity. It's not like we're driving in the middle of the Sahara with no a filter at all. Anyway, I was just looking for ways to improve my mileage (with the price of premium steadily going up) and was wondering if anybody had any experience with high flow exhaust/filter combinations (if it had any effect at all). Thanks again guys!

[Victor]

One thing I forgot to mention. Your engine oil will turn pitch black if you use a K&N air filter because it lets in so much dust, particularly if you are lax at cleaning and re-oiling it. If you are lazy use the original equipment type paper filter.

[driverdriver]

I've been running a drop in K&N filter for many years. Any performance gain/mileage gain is really dependent on the overal health of your vehicle. I haven't had any issues.

[dcat151]

I'll second this. I've been running a K&N drop-in filter for over a year with no issues.

[#1 Sailor Scout]

I'l chime in a 3rd thumbs up for the K&N filters.

It all depends on what you are looking for. The drop-ins will work great with the J30. Gas mileage will increase slightly, as well as your throttle response. You do have to keep them clean, though.

If you want a cone K&N, then go on ahead & get ready to make a custom CAI. They do not work well with them just sitting inside of the engine bay, especially with no heat shield around it.

I don't know about the exhaust deal as far as MPG gains go, but if done properly, they can make the J sound really mean. I think gr8scott had a custom exhaust on his J & it sounded like a muscle car IMHO. Just pure evil sounding.