Yes I live in Germany, I average 25MPG in my car which isn't *all* that bad - luckily 70ltr tank means I can usually get > 300 miles on autobahn. Tyre wear is also pretty dramatic especially with winter tyres on... It doesn't bother me too much since it's a company car and I have a fuel card, I did maintain fuelly with the m240i as I was curious - I got to as low as 18MPG on a tank, but the ZF 8 speed even if it locks in 7th in sport is geared so long that the B58 isn't even that bad.
I drive the A8 regularly, I find that I can do 150ish km in 1hr instead of the 1h30 that navi/google recommends if you go flat out in quiet day time. I usually slow down a bit at night as I've had a few surprises and if I go long distance I stick to something more reasonable (220ish) - I find it quite tiring for long drives to maintain really fast speeds and cabin noise gets a bit annoying about 220 unless you're on your own with music blaring out.