Well, there was a lot of highway driving, yes, and it was in line (so air, drag etc maybe?) BUT there was plenty of seaside roads which go up and down and side to side....i wasnt going too slow either.
SOO, my hypothesis is.....I dont know
In the hills, pushing it HARD HARD HARD, i manage to clock up 22L/100
A tip to everyone here though, if on a highway just jump behind a bus/truck and slip steam them. For about 10km i was behind a truck and we were both on cruise control perfect, the car was about 20 vac just cruising at 100km/h and every time i or he drifted, i could feel the massive walls of air....it was pretty cool (yet, somewhat dangerous)