winter gas, elevation, speed, wind, amount of cargo, tire pressure, terrain all play a role in gas mileage. These threads always come up in winter and kind of disapear in the summer. I was just talking about this subject with my neighbor ( he drives a nissan murano 100 miles a day to and from work almost all highway ) and he says he loses about 3 mpg every winter because of winter gas. Go to the f150 ecoboost forums, there are a ton of threads over there about their gas mileage as well ( ecoboost is very speed sensitive as well ) they aren't doing much better than we are!!