Welcome to the North American Subaru Impreza Owners Club Monday July 22, 2019
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > FA Series Factory 2.0L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 02-18-2019, 06:05 PM   #1
GalwayIrish
Scooby Newbie
 
Member#: 469092
Join Date: Jun 2017
Default Gas mileage calculations

Looking to see if it's just me...

I have noticed that on my 2017 WRX (stock) that the digital display center gas mileage is consistently 8% - 9% higher than my traditional calculations:

1) Not related to summer/winter gas changeover (i.e., all in one season)
2) Same gas station, self-service, same pump, same 93 octane, no top off (i.e., end when pump clicks off).
3) Same lower "actual" mileage over several months.

I had the same issue on my 2007 Legacy GT. If I remember correctly, Subaru got spanked by the Feds for bogus EPA mileage numbers (too high). Maybe coincidence, maybe conspiracy.

In any event, any one else's results?

Thanks.
* Registered users of the site do not see these ads.
GalwayIrish is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 02-18-2019, 08:13 PM   #2
Sillo
Scooby Specialist
 
Member#: 423270
Join Date: Jun 2015
Chapter/Region: Tri-State
Location: Long Island
Vehicle:
2015 WRX (sold)

Default

Yup, seems to always be over estimating by 3-4 MPGs.
Sillo is offline   Reply With Quote
Old 02-18-2019, 08:30 PM   #3
curiousfish
Scooby Specialist
 
Member#: 89283
Join Date: Jun 2005
Chapter/Region: Tri-State
Location: Queens, NYC
Vehicle:
2017 WRX Premium
ISM

Default

agreed, mine usually calculates to 2-2.5MPG higher (2017 WRX stage 2+ protuned)
My 2008 WRX and my wife's 2011 Impreza 2.5i reads 1-1.5 MPG higher.
curiousfish is offline   Reply With Quote
Old 02-19-2019, 06:14 AM   #4
rtv900
Scooby Specialist
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

mine is pretty accurate, not a wrx but still, you'd think the system that calculates it would be the same.
mine is within .5 probably

Plus, I feel like they grossly underestimated the potential mileage of the STI. Obviously the turbo allows you to blow through fuel like it's going out of style, but I just did a 150 mile round trip on the turnpike where it's mostly flat and I was in no hurry and did about 60 or maybe 65 the whole time, no passing, etc.
Legit got 28 mpg door to door.
rtv900 is offline   Reply With Quote
Old 02-19-2019, 09:41 AM   #5
CGumina
Scooby Newbie
 
Member#: 459394
Join Date: Dec 2016
Chapter/Region: Tri-State
Location: Rochester, NY
Vehicle:
2015 WRX
Crystal White

Default

Mine has never been accurate; it's always some 3-4mpg "hopeful" compared to reality. I use it more like a "how gentle have I been to the car this week" meter more than anything else.
CGumina is offline   Reply With Quote
Old 02-19-2019, 10:13 AM   #6
anarekist
Scooby Specialist
 
Member#: 468117
Join Date: May 2017
Chapter/Region: SCIC
Location: Southern Cali
Vehicle:
2017 WRX
DMG

Default

since going flex fuel im mpg has gone way higher but i fill up more often, i know e85 doesnt have the best mpg so im pretty sure it's wrong as hell now.
anarekist is offline   Reply With Quote
Old 02-19-2019, 11:30 AM   #7
WRXnick16
Scooby Newbie
 
Member#: 447898
Join Date: May 2016
Location: Sacramento, CA
Vehicle:
2019 STI
Crystal White Pearl

Default

Quote:
Originally Posted by anarekist View Post
since going flex fuel im mpg has gone way higher but i fill up more often, i know e85 doesnt have the best mpg so im pretty sure it's wrong as hell now.
Same here. I calculated my mileage on E50 over 3 tanks.

The display indicated an average of 36.5 mpg with a max of 43 mpg. My calculated gas mileage was 24 mpg.

This means that my display is overestimating by ~40% on E50. This would put my calculated peak highway mileage at ~29 mpg! Even though the display is overly optimistic, these numbers are still very respectable for ethanol IMO. This is basically what it was rated for stock on regular fuel.

I plan to do the same test on 91 at some point for comparison, but it's hard to go back to 91 after experiencing ethanol.

Last edited by WRXnick16; 02-20-2019 at 12:07 PM.
WRXnick16 is offline   Reply With Quote
Old 02-19-2019, 12:06 PM   #8
rtv900
Scooby Specialist
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

I have a hankering for some ethanol in the form of a cold barleywine
rtv900 is offline   Reply With Quote
Old 02-19-2019, 02:36 PM   #9
Charlie-III
NASIOC Supporter
 
Member#: 30669
Join Date: Dec 2002
Chapter/Region: Tri-State
Location: USA, North NJ, 07456
Vehicle:
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

Default

Depends on the system, but in general (assuming stock fuel system, stock diameter tires), the calculator is a "best guess" with a number of variables unknown.
COBB Tuning had one in the AP (not sure if still in there), many years ago they made mention it is a guide, not absolute after similar complaints in this thread.

I just log gallons in, miles driven, there is my MPG.
Charlie-III is offline   Reply With Quote
Old 02-20-2019, 07:54 AM   #10
mball19
Scooby Newbie
 
Member#: 322749
Join Date: Jun 2012
Default

The computer in my 17 is optimistic too. It normally shows 29-30 after my typical driving and my average for 2018 was 27.5 mpg.
mball19 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 07:40 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2019 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.