Winter fuel, fluids that are as thick as honey, 4x4 engage, tire roll resistance, parts taking longer to warm up, a lot of cold weather variables will take there toll on vehicles MPG especially. I will say I love that at -40 the Eco does better than my last V8 and V10; especially when it is outside idling for a hour or so. Yes there is a bigger difference in the MPG from cold weather to hotter weather with the Eco but and my last motors I have had didn't differ as much but that is because they were always lower teens (V10 was in the low teens on a good day) where as the Eco give mid teens for winter and in the high teens to 20s come summer. I can live with such a trade off and from what I have seen every vehicle is these Sub arctic temps suffers massively.