Hi Maxx, welcome to the forum!
Many factors affect fuel mileage and in the winter most people see a decrease in their fuel mileage over what they normally see in the summer months. Other factors include dirty air filters, bad ignition components (plugs, wires, weak coils, etc.) and driving conditions and habits.
Another consideration is that E85 fuel yields less miles per gallon than unleaded gasoline. It might be better for the environment but it will kill you in the wallet!
Hope that helps some.
Mac