Just came back from a 72 hour trip to Wales and back - 832 miles total in our 2005 XC70 auto Geartronic D5 with 195K (almost 196K now).
The average trip meter mileage went from 49.2 (lots of short trips in the precious month) to 50.2.
Almost all was on two lane roads as I dislike freeways and a zillion of roundabouts so lots of accelerating and braking and accelerating and braking and accelerating - you get it - not exactly easy steady driving and a lot of it up the famous Wales hills.
On long trips on the continent we usually come back home with an indicated 55+(UK) mpg average - but then I am perfectly content setting the cruise at 62 mph and enjoy the scenery..
My previous 2002 V70 auto D5 produced very much the same mileage - even loaded to the gills with the sailing and boat gear we take with us.