Just done a long trip heading west across europe ,mostly motorway. . At plus 9C I was struggling to achieve 5.5 liters per 100 km (51 mpg) . Didnt often go into EV mode But later, when the temperature had dropped to minus 3C I managed 4.9 litres 57 mpg ,and a bit more often in EV .More like what I was expecting for the speeds in winter.
Cold battery is less efficient ,and cold air is more dense aerodynamically. So why was it better at minus 3 than it was at plus 9 ? No real difference in speed or terrain.
I noticed that when MPG was poor the windfarm windmills were going at a good speed and I could tell from their orientation that, for hundreds of miles, I was predominantly battling against a headwind. This was not noticeable as buffeting when driving, or strong enough to sway leafless trees.
Yet later when mpg improved to 57 mpg the windmills were largely dormant , so little wind, and what there was appeared to be a tail wind for me. I think had I been travelling in the opposite direction my mpg would have improved overall and typically averages out over time.
I cant claim it was all due to wind direction as the poor mpg section did include some heavy rain which may have also increased tyre rolling resistance.