Interesting thread!
I just had a A4 B9 saloon demonstrator - 2.0 TFSI S-Line w/ 18" wheels, and the MMI would show just shy of 50mpg on a very gentle motorway run for my best.
My commute is from around Brighton - Heathrow, 140m per day (120 on m-way).
I got through a tank (to red line) in around 450 miles, so 41mpg. I did have a few "spirited" drives with that fill too!
TBH I would have expected a little better, but expect it to improve with time as car only had 1500 miles on the clock.
In efficiency mode you could see revs drop down when coasting, or going downhill! Smart