I changed out my stock air filter with a K&N Air Filter and now I am getting less mileage per tank of gas Can anyone tell me why this is.

 

Just an air filter, or the whole FIPK kit?

If its the kit. You could be changing your driving habits for the sound. Also it is winter and winter gas sucks, how often do you calculate your MPGs?

 

because your getting more/additional airflow, so the ecm is adding more fuel to keep the AFR in line....

get a tune to get your fueling dialed in correctly...

 

please dont do this right away, first, answer chibi's question, if your driving habits changed, that's definitely the reason, if you drive the same then theres more to look into

 

I blame the winter gas mixture. My fuel mileage always goes down by 1-2 mpg from Nov through March.

 

The fuel mix in the winter is always suspect, additionally if you are in the colder areas you are likely allowing your car to warm up on cold mornings - at least you should be! The extra idling uses extra fuel don't forget. I lose 1 average mpg easily in the winter, sometimes more.

 

Thank you for the helpful responses. I only installed the square K&N air filter that goes in the stock air filter box. I really do not feel that my driving habits changed. I only installed it because I was told that it would improve my MPGs. I did not know that winter would effect the MPG so maybe that may be my culprit. I do let the car warm up when it's cold so I'm probably losing some there. Would a tune up like 06Monte recommended be my next step?

 

I would honestly wait until the weather is nicer and you aren't warming up the car, using winter gas, etc. etc.

Most people lose a good amount of MPGs in the winter because they warm up the car, brake more and accelerate more, etc. etc.

The K&N replacement won't honestly give you more MPG over a clean air filter. The joy of that air filter is that you can clean it, oil it, and re-use it. So you keep a cleaner filter longer and THAT helps your MPGs.

 

Thanks again everyone for the help. I appreciate it. Chibi, how often do you oil your filter?

 

The box my filter came in recommended every 50k miles. I clean it more often than that just because of the tennessee valley and all elements that come in hand with that.

Id say that the k&n filter does help performance therefore does help mpg, just not in an extremely noicable amount.