The winter gas definitely has
The winter gas definitely has something to do with it, but the ecoboost just doesn't like the cold for sure. I've had mine for one year this month so this is the first winter I've driven it in. I live up in Canada and we've had some really cold weather this year. My average this winter is around 14.5L/100km or 16 US MPG, 90% highway. In the summer time I easily average 11L/100km or 21 US MPG. I've always expected a drop in fuel economy in the winter but this engine is nuts. I've tried using the engine block heater and it doesn't effect the economy at all.