Installed K&N and MPG decreased...thoughts?

[evilstib]

I did a drop in K&N. PArt no: 33-2367 (off the top of my head).

I usually get ~25-26 mpg on the highway with my Dinan Stage II 135i.

It was 25 on the way down to Edmonton on Thursday night.

I installed the K&N this morning and drive back. It's ~300 miles and my mpg was 24.

Only delta I can think of is temp. Would have been ~+8C on Thursday evening and it was +1C on the way back.

Any thoughts? I paid $95 CDN for the filter....will return if I'm going to lose gas mileage. Isn't K&N supposed to increase gas mileage?

[TP 135i]

More uphill elevation on the way back.
Try doing the exact same route, not backwards.

[evilstib]

I've gone both ways twice in the prior 2 weeks. Fort Mcmurray is 370 meters elevation, edmonton is 668. It was down hill on the return where the mpg was lower. ;(

[evilstib]

Nice thought though. I wouldn't have thought about elevation difference. Could be a head wind as well....but usually it's ~25 mpg both ways.

[BuckarooVT90]

I wouldn't sweat 1mpg... what were your tire temps and tire pressures? was there traffic, did you follow behind any cars/trucks.... Too many variables to try to account for to try to create a calculation of less than 1mpg error....

[evilstib]

My main concern...why pay $95 cdn for no hp gain, loss of fuel and possible dirtier engine....any other thoughts?

[sb335is]

your ECU might not have adapted until the end of your drive.
I've got the same set up and had it on since ~200 miles.

[ErvGotti]

When I do MPG calculations I use the same strech of flat road and do 70 in 6th gear with cruise control. Try using cruise contol it'll give a more accurate reading.

[evilstib]

It was on cruise other than passing ppl. I passed fewer people on the way back than the way there.

I thought about the ECU adapting...should I unplug the battery, leave for a min and plug back in? Will I throw any codes if this happens?

[Canexican]

You are probably losing mileage because your ECU is throwing in more fuel to adjust for the increased airflow. Then again, i'm not 100% sure about that simply because N54's use MAP sensors vs MAF, so I don't know if the increase of incoming air is going to throw off the fuel trims enough to notice a MPG change.

I wouldn't whine too much about 1mpg...I average 10-12mpg on E85, haha...and mine's a 2 liter.

[1speedbike]

With just 1 mpg I'd agree with most people saying it's either a slight elevation difference, the ECU adjusting, or even wind. Which way's the wind blowing? If you went against it more on the way home but with it more on the way there, that could be the 1 mpg difference. Also, staying behind cars / trucks will increase your mpg too, so that's another variable that goes hand in hand with wind.

[RPM90]

Were you perhaps testing the new filter by doing more and harder accel runs to see if you felt something?

It only takes a few hard full throttle "tests" to bring your MPG down.

Also, don't use the computer. Use the simple manual calculation method.

One more thing, a 10F degree temp drop will lower tire pressure by 1psi.
Lower tire pressure, plus some testing runs, equals slightly lower MPG.

[babyboss]

performance filters is for PERFORMANCE gains not fuel saving , guess filter manufaturers try 2 buy both share of markets - Fuel Saving tactic & Performance .. so they get us all 2 buy ..