Not used the instantaneous readout on the 1.4Ecotsi but I would certainly expect a bit more from mine at that speed on a motorway run - say 45/47 at 75/80. Could be influenced by what tyre pressures you are using or whether the AC is on. I have climate on mine, but whether that is more or less efficient than the basic system I don't know.
I checked yday, front tyres were 38.5 and rears 35

