As above, generally within a couple of %, quite phenonmal how thay achieve this, I guess the injection pump meters the fuel and this is totted up against miles covered.

Still impressive mind.

My computer reading is within 1mpg (lower) of my full to full tank calculation. Some people do report a considerable exaggeration.

Mine is now always within 0.5mpg of the actual figure by using fuelly, it however came out of the factory reading 5mpg optimistic.

Slightly surprisingly, mine seems to be delivering within about 2% on trip mpg in mode 1!

Mine is now always within 0.5mpg of the actual figure by using fuelly, it however came out of the factory reading 5mpg optimistic.

I assume you can tweak the accuracy using VCDS? Is this the only way to do it?

Slightly surprisingly, mine seems to be delivering within about 2% on trip mpg in mode 1!

How do you know that? Driving a whole tank without stopping (for more than two hours anyway!) I guess?

I assume you can tweak the accuracy using VCDS? Is this the only way to do it?

Yes, to my knowledge VCDS is the only way to calibrate it.