lying gas mileage?? - Focus Fanatics
Ford Focus Forum
HomeContact UsAbout UsGalleryDiscussion ForumsMarketplace


Go Back   Focus Fanatics > Ford Focus Third Generation > MK3 Focus

MK3 Focus The place to chat about general questions, window tinting, exterior body, interior and lighting upgrades for the third generation 2012-Current Focus.

Search This Forum | Image Search | Advanced Search    
Ford Focus Tire & Wheels FocusFanatics Merchandise

Reply
 
Thread Tools Display Modes
Old 07-07-2013, 09:20 AM   #1
GreyBullit
Focus Enthusiast
 
GreyBullit's Avatar
 
Join Date: Jun 2013
Fan#: 115516
Location: Port Charlotte, FL
What I Drive: 2013, sterling grey,SE

Posts: 65
FF Reputation: 1 GreyBullit Good Standing Member
Buy-Sell-Trade Rating: (0)
lying gas mileage??

Has anyone calculated their gas mileage?? when you fill the tank, you divide the miles you used by the gallons you put in correct?? well, if that is true I'm only getting 20 mpg, but the computer says I'm getting 24 mpg. I now the car is barley broken in, 1090 miles on it, but that's the second tank that I counted and got a lower reading then the computer states..


__________________
2013 sterling grey Focus SE, tinted windows, in-channels wind guards, air box snorkel delete,Green Filter, chrome kick plates. More mods to come...
03 Honda Odyssey
GreyBullit is offline  
    Reply With Quote
Sponsored Links
Advertisement
 
Old 07-07-2013, 09:31 AM   #2
redzone
Focus Enthusiast
 
Join Date: May 2013
Fan#: 114512
Location: toronto, Canada
What I Drive: 2013 Blue Candy Hatchback SE

Posts: 138
FF Reputation: 1 redzone Good Standing Member
Buy-Sell-Trade Rating: (0)
i use fuelly to track my mileage. use trip 2 for all time avg mpg and trip 1 for each trip.

so far the computer has been preety much dead on.
__________________
2013 Focus Hatch Se
Blue Candy
Build Date: 03.02.2013
Stock for now
redzone is offline  
    Reply With Quote
Old 07-07-2013, 10:03 AM   #3
Elizabeth
Focus Fanatic
 
Elizabeth's Avatar
 
Join Date: Aug 2011
Fan#: 89280
Location: SouthEast, WI
What I Drive: '12 Yellow Focus SE stick, 17"rims

Posts: 2,780
FF Reputation: 14 Elizabeth Great Standing Member
Buy-Sell-Trade Rating: (0)
Better sell it now before you find out other naughty things your car is doing!
Little lies add up. You car is probably sleeping with that hot car down the street...
That hot rod is syphoning your gas on the sly...
I get 33 mpg all the time..
Elizabeth is online now  
    Reply With Quote
Old 07-07-2013, 10:06 AM   #4
joshuafail
Focus Enthusiast
 
joshuafail's Avatar
 
Join Date: May 2013
Fan#: 115261
Location: Brookline, MO
What I Drive: 2013 Ingot Silver SE w/MFT

Posts: 308
FF Reputation: 9 joshuafail Good Standing Member
Buy-Sell-Trade Rating: (0)
My first two or so tanks were way off from what the computer said I was getting. After that, it's been within .5 mpg.. Have you been resetting the meter ever time you fill up?
joshuafail is offline  
    Reply With Quote
Old 07-07-2013, 10:14 AM   #5
2kwik4u
Focus Enthusiast
 
Join Date: Aug 2012
Fan#: 102523
Location: Louisville, KY
What I Drive: '12-Sonic Blue-5dr/5spd/203A/Roof

Posts: 319
FF Reputation: 1 2kwik4u Good Standing Member
Buy-Sell-Trade Rating: (0)
ROFL at Elizabeth's post above! I love it!

The MPG meter in my car is only accurate around 30mpg or so. As you move away from that number the error increases. I have data for the last 21k miles to show if you like. My error wasn't quite as bad as the 20% off you are reporting, but it is noticeable. Error compounds if you aren't consistent in how you "top off" the tank as well. Two clicks after it shuts off automatically will create more error than if just letting it shut off on it's own, and then removing the nozzle.

As a reference for how the computer figures mileage. It takes the readings from the car, and computes the "average mpg" from that. Distance travelled since reset can be off by 3-5% depending on how accurate your speedometer is, of course that is impacted by proper inflation. Also actual fuel flow rate vs commanded is always off a little as well, leading to more error in the calculation. Even your hand calculations are a little "off" due to the gas station measuring volume not mass, and any error in that reading.

To get a "true" mpg number you need to compare mass of fuel actually used, vs Accurate GPS distance numbers. That will reduce the calculation error about as much as possible outside of a lab.

The moral of my story.......Don't trust the computers calculations, trust your hand calculations, and be as consistent as you can with your filling procedure. Using the same pumps helps too. It's worth checking your speedo's calibration with a decent GPS unit as well if you want to add in a correction factor for that.
2kwik4u is offline  
    Reply With Quote
Old 07-07-2013, 10:29 AM   #6
dan50
Focus Addict
 
Join Date: Nov 2011
Fan#: 91789
Location: Too much info, IL
What I Drive: 2012 SEL White Platinum 5 Dr 302A

Posts: 1,155
FF Reputation: 11 dan50 Great Standing Member
Buy-Sell-Trade Rating: (0)
The car's mpg computer is pretty accurate in my experience. The challenge in manual calculations is getting the tank to the same level of fullness each time. With a tank as small as on the Focus, a 1/2 gallon difference between fill can make a noticeable difference in mpg. Keep track of actual fuel consumed versus what the trip computer is thinking over 5 - 10 tanksful and you'll feel better.
dan50 is offline  
    Reply With Quote
Old 07-07-2013, 10:35 AM   #7
RonMaiden
Focus Fanatic
 
RonMaiden's Avatar
 
Join Date: May 2012
Fan#: 99230
Location: Littleton, CO
What I Drive: 2012 Red Candy Metallic Hatch SE

Posts: 4,076
FF Reputation: 6 RonMaiden Good Standing Member
Buy-Sell-Trade Rating: (0)
I find its good to reset the computer from time to time but for the most part with nearly all city and a little hwy we've been getting a solid 29 but has been as low as 25 for a tank or two. I'd be more concerned about only getting 20mpg in the first place.
__________________
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch
RonMaiden is offline  
    Reply With Quote
Old 07-07-2013, 11:43 AM   #8
darkangelism
Sonic Crew #04
 
darkangelism's Avatar
 
Join Date: May 2011
Fan#: 85425
Location: oklahoma city, OK
What I Drive: 2012 Focus Titanium Hatch

Posts: 7,306
FF Reputation: 9 darkangelism Good Standing Member
Buy-Sell-Trade Rating: (0)
Quote:
Originally Posted by 2kwik4u View Post

The MPG meter in my car is only accurate around 30mpg or so. As you move away from that number the error increases. I have data for the last 21k miles to show if you like. My error wasn't quite as bad as the 20% off you are reporting, but it is noticeable. Error compounds if you aren't consistent in how you "top off" the tank as well. Two clicks after it shuts off automatically will create more error than if just letting it shut off on it's own, and then removing the nozzle.

As a reference for how the computer figures mileage. It takes the readings from the car, and computes the "average mpg" from that. Distance travelled since reset can be off by 3-5% depending on how accurate your speedometer is, of course that is impacted by proper inflation. Also actual fuel flow rate vs commanded is always off a little as well, leading to more error in the calculation. Even your hand calculations are a little "off" due to the gas station measuring volume not mass, and any error in that reading.

To get a "true" mpg number you need to compare mass of fuel actually used, vs Accurate GPS distance numbers. That will reduce the calculation error about as much as possible outside of a lab.

The moral of my story.......Don't trust the computers calculations, trust your hand calculations, and be as consistent as you can with your filling procedure. Using the same pumps helps too. It's worth checking your speedo's calibration with a decent GPS unit as well if you want to add in a correction factor for that.
This, calculating your own is much better than the computer calculation.
darkangelism is online now  
    Reply With Quote
Old 07-07-2013, 12:08 PM   #9
Von551
Focus Enthusiast
 
Von551's Avatar
 
Join Date: Jun 2013
Fan#: 115392
Location: san diego, CA
What I Drive: 2013 Focus SE Hatchback

Posts: 117
FF Reputation: 1 Von551 Good Standing Member
Buy-Sell-Trade Rating: (0)
take it in to get looked at. i only have 1,500 miles on my car and am already averaging 29mpg with aggressive manual transmission driving. computer was spot on to my hand calculating of mpg when I filled up last night. unless you ONLY drive city and keep if floored all the time, your computer/math is way off. you should get high 20's, low 30's easily.
__________________
2013 Focus SE Hatchback, White, MT, SE Appearance Package, Black Rims. AKA "The Oreo"
Von551 is offline  
    Reply With Quote
Old 07-07-2013, 01:10 PM   #10
raptor1956
Focus Addict
 
Join Date: Apr 2012
Fan#: 97725
Location: Taylorsville, UT
What I Drive: 2012, Sonic Blue, Focus Titanium

Posts: 1,193
FF Reputation: 1 raptor1956 Good Standing Member
Buy-Sell-Trade Rating: (0)
My computer is within 0.5% of true mpg and has been since day one. I see a tank-to-tank variation in hand calculated mpg that I conclude is due to a nominal +/-0.5 gallon variation in tank filling that results in a difference between the cars computer and hand calculation of +/- 3mpg.

But, if you're getting down near 20mpg you are either sitting in stop-and-go traffic all the time or you are playing street racer -- there's no way that normal driving would result in mpg that low.

My lifetime average is 38.8mpg and I just turned over 20,000 miles. The lifetime average of the cars computer is 38.6mpg so that makes the difference 0.5% -- pretty decent if you ask me.

Lastly, since you can have more than a +/- 0.5 gallon difference in tank filling you can't make much of the results until you're able to average several tanks, like 5 tanks average.


Brian
__________________
2012 FF Ti HB Sonic Blue, Built 5/7/12, 401A + Parking Technology Package and MFT w/NAV 3.0.2 -> 3.2.2 -> 3.5.1 -> 3.6.2
raptor1956 is offline  
    Reply With Quote
Reply

Bookmarks & Social Networks

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 -5. The time now is 05:33 PM.


Copyright 2002-2014 FocusFanatics.com. All Rights Reserved : Terms of Use : Privacy Policy : Advertise Information : Site Map

Focus Fanatics Ford Focus Forum offers many fun ways for you to engage with other Ford Focus Owners from across the world. Whether it be about the aftermarket performance modifications, technical how-to's, European tuned suspension or awesome fuel economy similar to the Acura TLX or Fiesta ST. You can find all Ford Focus and Focus ST related information here. Join our Ford Focus discussion forums and chat with local Focus enthusiasts in your area.