I recently swapped my stock exhaust out for ARK catback exhaust. Since my mileage has gotten worse. Any ideas? I know partially could be due to wanting to hear that sweet sound more in the revband but I haven't been driving it that much differently.

Any thoughts?

 

Did you reset the ECU?

 

Nope. You think that may help? Is that the battery terminal off deal?

 

Winter blend fuel causes gas mileage to worsen. Cooler temps will make mileage worse too.

 

lol, i am suffering from same exact issue. I installed Ark Grip on my 2012 sedan and my mileage dropped from 20-22mpg to 15-17mpg. I reset the ecu couple of times, drove super old grandma like and still couldn't come close to 19mpg.
This is what i am testing these days and I have no idea why its working, I tried regular 87 gas instead of premium 93. 1st tank gave me solid 21mpg. I am on my 2nd tank, used a quarter and still getting about 21-22 mpg. I have no idea why regular is giving me more milage now. scratching my head :/
i will try premium again after this tank to confirm this... its very weird lol

 

there is a youtube video showing how to do it without battery take off, super easy! search "g37 ecu reset"

 

May not be the exact fix but it's something you need to do regardless so your computer can adjust

 

Wow ... Never thought of that LoL... Just curious any I'll effects or issues since running 87 Octane?

 

That's kind of weird....

I put on a Stillen cat back in July and have not noticed any difference in fuel economy... I average 20-21 mpg while "enjoying" my exhaust

Don't get you hopes up on "resetting the ECU"... it won't make a difference. This is an old internet myth. The ECU adjust all the time to compensate for changing environmental factors (air pressure, temperature) fuel quality, etc.

It could be a simple as the arrival of winter gas.

 

car feels slower in acceleration according to butt dyno.
2nd gas tank 1/2 now. getting 20.8 mpg. its very good for me, not pushing the car. just driving normally.

 

So no other issues though? Engine knocking etc?

I normally always have used 91 but for some odd reason since my ARK Grip Exhaust install I've been getting exactly that 15 mpg even when driving very normally ... almost all city driving but prior i was getting about 17 mpg.

It's not the price per tank I'm worried about ... just the worse mileage .. any ill effects for running 87 Octane?

 

^This

Your ECU only changes your fueling, spark, and air intake. And it monitors the air:fuel ratio, and knock sensors to do all 3. Your Cat-back exhaust system is downstream from the last o2 sensor, so to be quite frank; in regards to your ECU, nothing has changed whatsoever.

What you're most likely experiencing, is a combination of winter blend gas, and rev-happiness. Although even then, thats a pretty decent hit in MPG.

 

Are you actually doing the math or relying on the cars fuel economy display? Also do you have any exhaust leaks?

 

It's because your car sounds badass now so you can't help but put in a little more gas

 

I'm going by the Fuel Economy Display. I'm hoping no exhaust leaks ... How can you usually tell?.. Smell? Sounds?