1.6 mjet diesel station wagon, and I do a regular 170 mile journey which is mainly motorway, and last few runs in mpg were:-
68.2
64.6
69.6
69.6
All on Tesco diesel, and with one short stop each journey.
Figures from trip computer, but they seem to reflect reality. Journey is around 20 miles A road 150 miles motorway, with probably about 1/3 of that in some form of speed restriction, either due to congestion or miles and miles of roadworks!! Therefore a big chunk is done at 50mph with cruise control on which makes the figures look better of course.
Not measured so carefully elsewhere but local running get a more typical 47mpg which is an approx.