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MPG downgrade after replacing the air filter

1075 Views 5 Replies 4 Participants Last post by  Dork Knight
I changed the air filter with a K&N oiled filter on my 2006 330i. After noticing that the MPG in city is even not as good as when I used the old filter which runs about almost 100k miles..... Few days later I gave up on the K&N filter and replaced with my old filter, however, the MPG doesn't go back. Now I have a almost 15~16 MPG in city which is unusually low. Last year, I can have a almost 20~22 MPG in city.

I don't know which part goes wrong with my car, is it because the MAF sensor got damaged by the oil or because there is some sort of leaking in the intake system?
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You should have researched before getting K&N. I had the same experience with my 06 330xi, my MAF went bad and costed $500 to repair.
You'd get check engine light with code that says it's burning too rich. If you're DYI use CRC MAF cleaner that can be bought in local auto shop also.
http://www.amazon.com/CRC-05110-Mas...id=1343706874&sr=8-1&keywords=crc+maf+cleaner
I went back to OEM filter.
Come on guys are you serious. 4 mpg loss! I guess we are all perfect these days and have no room for marginal error...?

maybe during your fill-up, the car had several fewer ounces of gas then when you filled up prior to your filter change. Or maybe the pump pumped several ounces fewer than your last fill up. I mean come on i can keep going all day to make up reasons for your 4mpg decline.

At the end of the day its a car and its performance will vary based on many varying conditions, so just chill out and enjoy it for what it is, a fun car to drive!
Thanks man. I've ordered this MAF cleaner and hope it will go well.
You should have researched before getting K&N. I had the same experience with my 06 330xi, my MAF went bad and costed $500 to repair.
You'd get check engine light with code that says it's burning too rich. If you're DYI use CRC MAF cleaner that can be bought in local auto shop also.
http://www.amazon.com/CRC-05110-Mas...id=1343706874&sr=8-1&keywords=crc+maf+cleaner
I went back to OEM filter.
Thanks! I guess you are right, the thing I need to figure out is hope the the K&N filter doesn't damage my MAF sensor.
Come on guys are you serious. 4 mpg loss! I guess we are all perfect these days and have no room for marginal error...?

maybe during your fill-up, the car had several fewer ounces of gas then when you filled up prior to your filter change. Or maybe the pump pumped several ounces fewer than your last fill up. I mean come on i can keep going all day to make up reasons for your 4mpg decline.

At the end of the day its a car and its performance will vary based on many varying conditions, so just chill out and enjoy it for what it is, a fun car to drive!
I read an article awhile back that said K&N was substantially more hype than a proven performance benefit. I'd have to search out the study again, but I've yet to buy a K&N since.
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