Computer MPG vs Hand Calc after the fix

tsspencer2887

Member
Joined
Mar 23, 2016
Location
Texas
TDI
2011 Jetta Sportwagen
This may be an old topic but I didn't find anything about it. If so, please refer me to that thread and delete this one.

I had the fix on my 2011 Sportwagen 6MT a few weeks ago but I haven't been the one to refill the tank yet. Others in my family have taken it on some long road trips but they don't know how to reset the computer. Prior to the fix, the computer showed ~1-1.5 MPG higher than hand calc. My Dad drove the car on a trip a week ago and swears that I'll be lucky to get 40 MPG now. However I took it on a short trip (~150 miles) and the computer's MPG had me averaging ~48-49 MPG.

I'll know how far off the computer is the next time I fill up but I don't know when my next long range trip will be. Is there any reason that the computer should be further off now than it was before? Just wondering if anyone has noticed a difference.
 

jbright

Veteran Member
Joined
Sep 10, 2009
Location
Indianapolis
TDI
2009 Jetta DSG
I have recorded both computer averages and hand calculated averages per tank since buying my 2009 new. After the fix (in October), the computer is off 2 to 4 mpg (higher than hand calculated) vs .5 to 1.5 before. This is all based on routine mixed driving in Indianapolis. It will be interesting to do a long highway trip and see the numbers then.
 
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Blue_Hen_TDI

Top Post Dawg
Joined
Oct 23, 2005
Location
Slower, DE
TDI
owned: 96 B4V, 06 Golf, 12 NMS, 15 GSW
I’m a different TDI model & generation, but the MFD on mine typical shows 2 to 2.5 mpg (roughly 4%) higher than actual, and I record every tank on Fuelly. I haven’t tried correcting with VCDS because it’s not that important to me honestly.
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
It is possible but only you will know when checked. If you are near Austin I have VCDS and we can reset it so it shows near actual once you find the setting you need. Who really cares what the computer says if it is wrong? Take some trips and find the number and get it reset so its closer. All highway vs all city will show different results as well in my experience.
 

Smashed Ixnay

Veteran Member
Joined
May 7, 2010
Location
Auburndale, FL
TDI
2015 Passat TDI SEL
Only had a 2010 Jetta TDI and it was 0.5-1mpg off without the fix. My new 2015 Passat TDI with the fix is 2-4mpg off from what I've noticed, but I haven't had a true full fill up. Right now I have 2 more days of driving and I'll have to fill up. Assuming nothing happens between now and then, I'll be able to give a real answer.
 

tsspencer2887

Member
Joined
Mar 23, 2016
Location
Texas
TDI
2011 Jetta Sportwagen
Thanks for the input. All of my day to day driving involves rush hour traffic in DFW (aka "the metromess"). So I typically average 36-37 MPGs (hand-calc). However, we have a trip coming up to Florida next month and are deciding between taking my Jetta or my mother's far more comfortable yet much less fuel economic ML350.
 

Q5TDI

Veteran Member
Joined
Jul 10, 2017
Location
US
TDI
Q5
How does the computer calculate the mpg and mileage left before an empty tank?
When I would fill up my 2014Q5 TDI pre-fix, the computer would often tell me I could go 650 miles before the tank went empty. I would be lucky to go just over 600 miles in most cases, and in several cases, I could only go 500-525 miles.

Still, by hand calculation, my TDI consistently got 29-31 mpg, which is what the computer would tell me for the overall mpg since I bought the car. I drive about 50/50 highway and around town.

I would never base mpg of the instantaneous mpg number, which can fluctuate between 5 mpg and over 200 mpg, depending on if the car is going uphill, downhill, accelerating, etc.
 

forrest resto`s

Veteran Member
Joined
Jul 8, 2007
Location
athens ga.
TDI
2000 jetta tdi auto rc2 2013 passat tdi 2015 passat tdi auto 2011 jetta tdi nav. s'roof..man. dpf delete 1970 GTO JUDGE 520 HP
This may be an old topic but I didn't find anything about it. If so, please refer me to that thread and delete this one.

I had the fix on my 2011 Sportwagen 6MT a few weeks ago but I haven't been the one to refill the tank yet. Others in my family have taken it on some long road trips but they don't know how to reset the computer. Prior to the fix, the computer showed ~1-1.5 MPG higher than hand calc. My Dad drove the car on a trip a week ago and swears that I'll be lucky to get 40 MPG now. However I took it on a short trip (~150 miles) and the computer's MPG had me averaging ~48-49 MPG.

I'll know how far off the computer is the next time I fill up but I don't know when my next long range trip will be. Is there any reason that the computer should be further off now than it was before? Just wondering if anyone has noticed a difference.
I never got 48 49 mpg's:eek: on my 2011 jetta 6mt..before the fix and surely not after.. on a road trip i may get 43 if I'm lucky...hand calc.
 

Smashed Ixnay

Veteran Member
Joined
May 7, 2010
Location
Auburndale, FL
TDI
2015 Passat TDI SEL
I just filled up and I ended up with 823.6 miles this tank. Odometer said 51.7mpg but hand calculated I got 48.5, which is in line with the 2-4 mpg difference I usually get. I did drive a lot slower and kept most of my speed at 70 mph and there was a few days I would do 65 on the way home just because I didn’t have to pick my daughters up and wasn’t in a rush.


I ended up driving about 8 miles once I hit 0 just bc I wanted to fill up at the same place. I know this car has an 18 1/2 gallon tank and usually the max I am able to put in there is 17 gallons so I wasn’t worried about driving a little once I hit zero.
 
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tsspencer2887

Member
Joined
Mar 23, 2016
Location
Texas
TDI
2011 Jetta Sportwagen
Filled up last night and the computer overestimated ~2 mpg. At least 75% of the tank was rush hour traffic. I ended up getting about the same as I averaged in the same traffic prior to the fix.
 

toneman

Veteran Member
Joined
May 6, 2004
Location
norcal
TDI
2011 JSW
Filled up last night and the computer overestimated ~2 mpg. At least 75% of the tank was rush hour traffic. I ended up getting about the same as I averaged in the same traffic prior to the fix.
I appreciate your comparative fuelly accounts - thank you. My 2011 JSW manual nets me ~31mpg in mostly city driving (yeah, I know) though it's been down almost 2 since I've left my roof racks on. No fix yet, part of the waffling undecided.
 

Quincy

Veteran Member
Joined
Apr 5, 2005
Location
Arlington, WA
TDI
2015 Passat SE TDI, 2007 Dodge Cummins QC 4X4 6 sp, 2007 John Deere 3120
I just filled up and I ended up with 823.6 miles this tank. Odometer said 51.7mpg but hand calculated I got 48.5, which is in line with the 2-4 mpg difference I usually get. I did drive a lot slower and kept most of my speed at 70 mph and there was a few days I would do 65 on the way home just because I didn’t have to pick my daughters up and wasn’t in a rush.


I ended up driving about 8 miles once I hit 0 just bc I wanted to fill up at the same place. I know this car has an 18 1/2 gallon tank and usually the max I am able to put in there is 17 gallons so I wasn’t worried about driving a little once I hit zero.
Is there a way to get the trip computer to run an average from reset to reset like every other vehicle I've ever had? My MPG is always started upon starting the car. It will continue the same trip if the car is stopped and started within a certain amount of time. I have always run the averages from fuel fill to fuel fill so I would know how inaccurate the computer is.
 

Blue_Hen_TDI

Top Post Dawg
Joined
Oct 23, 2005
Location
Slower, DE
TDI
owned: 96 B4V, 06 Golf, 12 NMS, 15 GSW
Is there a way to get the trip computer to run an average from reset to reset like every other vehicle I've ever had? My MPG is always started upon starting the car. It will continue the same trip if the car is stopped and started within a certain amount of time. I have always run the averages from fuel fill to fuel fill so I would know how inaccurate the computer is.
When you reset your trip odometer it resets the “mpg since refuel” readout.
 

joshuafail

Well-known member
Joined
Jan 25, 2018
Location
Springfield, MO
TDI
2015 Passat SEL Premium
Is there a way to get the trip computer to run an average from reset to reset like every other vehicle I've ever had? My MPG is always started upon starting the car. It will continue the same trip if the car is stopped and started within a certain amount of time. I have always run the averages from fuel fill to fuel fill so I would know how inaccurate the computer is.
On mine, once you’re on the “consumption” screen, click the “ok” button on the steering wheel to go from screen 1 to 2.

1 is the average for the trip, 2 should be average since last reset.
 

Quincy

Veteran Member
Joined
Apr 5, 2005
Location
Arlington, WA
TDI
2015 Passat SE TDI, 2007 Dodge Cummins QC 4X4 6 sp, 2007 John Deere 3120
I haven't come across in any of the books either. I'll get it out and make another run at it with fresh eyes. If anyone knows what page, I'd appreciate it.
 

Rico567

Top Post Dawg
Joined
Jun 13, 2003
Location
Central IL
TDI
2013 Passat TDI SEL Premium (Turned in 7/7/18)
Our Passat falls into the 2-4 mpg high MFI readout that several others in this thread have reported. Our average over nearly 69K miles, strictly hand-calculated from the pump receipt and odometer, is reported in the Fuelly below.
 

Blue_Hen_TDI

Top Post Dawg
Joined
Oct 23, 2005
Location
Slower, DE
TDI
owned: 96 B4V, 06 Golf, 12 NMS, 15 GSW
I believe I found the information in the big book on page 28.
Yeah, I couldn't help you on page numbering because I have a GSW.

I learned how everything works just by fooling around with the buttons and menus. Everything should be within thumb's reach of the steering wheel for these operations. I think there's also a quick-start guide inside the manual binder that may help.
 
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