Fuel consumption

[ahtcap]

2005 bkd
MPG on the dash show 16%/17% more than it actually is.Ive done numerous tank to tank refills and calculated the actual MPG.
Why is there such a large difference?
I know it can be altered using VCDS but only by 15%

 

[paddy]

wrong size wheels ?

 

[Darren92]

DIS is never accurate unless you adjust it.

 

[ahtcap]

wrong size wheels ?

Cars running on 17in wheels.

DIS is never accurate unless you adjust it.

17% error is a long way out!

 

[Daveyonthemove]

Remap or tuning box fitted?
On my last car the tuning box over exaggerated by 9-10mpg over a tank. When I removed it the figures became accurate again.
On the S3 I have found that the OBC is nearly always below the actual MPG on tank to tank calculations.

 

[ahtcap]

No tuning box,
Unaware of any remap, and no fault codes,
I just find it unusual that it could be so far out!

 

[paddy]

Have you tried logging the MPG on "2" over several tanks to see if it evens out. Short term mpg will vary on setting "1" a lot as it averages each trip, i dont know how setting 2 works but if its the same then your last logged trip on each set of tank to tank readings will have a disproportionate effect overall but this will average out the more tank fulls you add to the total
Try averaging your next 4 fill ups without resetting and see if its still 17% out

 

[ahtcap]

Have you tried logging the MPG on "2" over several tanks to see if it evens out. Short term mpg will vary on setting "1" a lot as it averages each trip, i dont know how setting 2 works but if its the same then your last logged trip on each set of tank to tank readings will have a disproportionate effect overall but this will average out the more tank fulls you add to the total
Try averaging your next 4 fill ups without resetting and see if its still 17% out

I use a full tank each week and compare it every time(very sad i know)done this since i bought it ( 4 yrs)

 

[paddy]

Yes but have you let the trip meter run on for 4 tank fulls.
for example if i get in the car a drive 1 mile it says 10mpg, if i drive 50 miles it says 30mpg, the bigger the sample the more accurate it will be.

 

[ahtcap]

Understand were your coming from , i just found it unusual to be so far out on one full tank.

 

[paddy]

maybe we should all do this and see how far our DIS is out ? I have never checked but i will next time i fill up. What has been very noticeable is that since i went stg2+ my fuel consumption has actually improved by a couple of mpg. I suppose the engine is just running more efficiently.

 

[Daveyonthemove]

Mine can be seen in the link on my signature.
I add a note to every fill up stating the OBC readout so i can get an idea of accuracy.

 

[ahtcap]

Going off your last 10 fill ups there is a 14.1% difference. Makes me feel a little better.

 

[Daveyonthemove]

I have never bothered to work out the percentage, but noting the OBC readout and comparing it to actual MPG, it's usually within 2 mpg difference every time, so I'm happy with the accuracy (especially as the car thinks I'm doing worse than I actually am).

 

[ahtcap]

Forget my calculation on yours as they are incorrect.