Gort Posted December 16, 2015 Share Posted December 16, 2015 Hello to everyone. I am new to the site and found valuable information for spark plug selection for my 2003 outback "mitchmobile" - THX. I did not find a similar discussion about air filters. My question is whether it is cost effective to buy the K&N air filter @ about $50 compared to a more conventional filter @ about $15? I am not looking for a high performance "rally" application - just to work and home about 70 miles a day. Does it improve MPG enough to warrant the high cost? Thanks to all for taking time to respond. Link to comment Share on other sites More sharing options...
Rooster2 Posted December 16, 2015 Share Posted December 16, 2015 Don't think a K&N air filter will help much with performance or MPG. If it were me, I would stick with the conventional type air filter that came with the Subie. 3 Link to comment Share on other sites More sharing options...
golucky66 Posted December 16, 2015 Share Posted December 16, 2015 Don't think a K&N air filter will help much with performance or MPG. If it were me, I would stick with the conventional type air filter that came with the Subie. Agreed. Unless you really need that extra 1-2 hp it doesn't make sense... How will changing the filter allow more air flow into the engine? By reducing the amount it can filter usually. Therefore allowing some things into the engine that the conventional would block. Not to say L&N filters are bad. But not recommended for regular drivers. Link to comment Share on other sites More sharing options...
mikaleda Posted December 16, 2015 Share Posted December 16, 2015 (edited) Ya, I'm not a huge fan of K&N filters, their a pain to deal with. Once you clean them you have to wait for them to dry and apply the correct amount of oil. I've actually lost power with them when I first started using one just because I over oiled it. I've also heared of these filters causing MAF sensor issues, wich may not affect your model if its the MAP bases system. Long story short, unless you are really serious about getting the most out of your car, I wouldn't suggest a high performance filter like K&N Edited December 16, 2015 by mikaleda Link to comment Share on other sites More sharing options...
keith3267 Posted December 16, 2015 Share Posted December 16, 2015 Stick with the OEM type filter. A low restriction filter could give you 1 or 2 extra HP under WOT (wide open throttle), but under any other conditions, the main restriction to air flow is the throttle. The computer will calculate the right amount of fuel to inject based on inputs from various sensors like the MAF, MAP, inlet air temp and feedback from the O2 sensors. Changing the air filter will not affect the air fuel ratio on a modern car like it did on old carbureted cars. But, the K&N filter is an oil impregnated cotton filter. The oil can and does migrate to the incoming air stream and then coats the MAF sensor. If you can't clean the MAF sensor yourself, then you will find this to be an expensive and frequent repair. The K&N is also suspected of passing more dirt into the engine and contaminating the oil. I don't know if it is true and if it is, if the amount of dirt will actually be significant enough to have a measurable effect on the life or performance of the engine. But I can tell you from experience (my son uses a CAI which has the same type of filter element as th K&N) that the MAF sensor needs frequent cleaning for the engine to run at peak efficiency. Link to comment Share on other sites More sharing options...
Gort Posted December 17, 2015 Author Share Posted December 17, 2015 Thanks to all - it will be a conventional filter for my "Mitchmobile". Link to comment Share on other sites More sharing options...
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