The good news is that I am now able to adjust the fuel gauge needle up an down via vcds. I have some more experimentation to do, and measuring (via Advanced measurements), but this puts me on the right track in the event that VW comes back and says that having 2-3gal of diesel left in the tank after the needle hits "0" is done by design, or that having the needle drop 1/16 from Full after 20mi of driving is normal. Any vcds adjustments would all be done of course, and if I do it, at my own risk specially given all the comment contributions above.
What I am experiment with is no different from what's described here:
http://www.myturbodiesel.com/wiki/mpg-gauge-correction-and-adjustment-mk5-mk6-vw/
(1) Offset for tank calibration values - Offset sensor 1: from -12.8l to +2l
Range is -12.8 to +8.
-12.8l is the factory default.
<0 moves the needle down.
=0 no change/movement
>0 move needle up.
+1 = needle moves up by ~1/16 up
+2 = needle moves up by ~1/8 up
I was also able to play with and adjust the MFD MPG reading to now be within +/-1 of the actual, vs ~+5 to +6 on the optimistic side from factory. That one seems like a safe change.
Thanks again for everyone who has and continues to post. I'll update this thread once I get an answer from the dealer on the current accuracy of the fuel gauge. I did find a similar person in the UK with the same issue (from another forum), and VW ended up replacing his pump due to faulty readings. Who knows, maybe there is an actual problem causing this on my car.
What I am experiment with is no different from what's described here:
http://www.myturbodiesel.com/wiki/mpg-gauge-correction-and-adjustment-mk5-mk6-vw/
(1) Offset for tank calibration values - Offset sensor 1: from -12.8l to +2l
Range is -12.8 to +8.
-12.8l is the factory default.
<0 moves the needle down.
=0 no change/movement
>0 move needle up.
+1 = needle moves up by ~1/16 up
+2 = needle moves up by ~1/8 up
I was also able to play with and adjust the MFD MPG reading to now be within +/-1 of the actual, vs ~+5 to +6 on the optimistic side from factory. That one seems like a safe change.
Thanks again for everyone who has and continues to post. I'll update this thread once I get an answer from the dealer on the current accuracy of the fuel gauge. I did find a similar person in the UK with the same issue (from another forum), and VW ended up replacing his pump due to faulty readings. Who knows, maybe there is an actual problem causing this on my car.