mbopp

Winter gas = less BTU per gallon.
Engine is cold = running richer until it warms up.
Lubricants are thicker until they warm up = more drag.
Tires aren't as soft = more rolling resistance.
Air is colder and denser = more air resistance to push through.
And if it's snowing you're pushing snow, travelling slower, and fighting traffic.

FLtroll

The winter blend fuel has definitely knocked my economy back some.

Diabo8c4

i lost a good 2mpg with my 5.4

redfred

For me, its a definite loss of at least 2 mpg during winter blend gasoline time

ClaySlayer

yeah it's more than just the gas (no winter blend here)...I get the best mileage between ~60-70 degrees. Any higher or lower and I lose a little.

johnwill

Wait. What?

Juice_man_86

Wow...can't believe no one mentioned the fact that the air pressure in the tires is lower in colder temps, unless you correct it. This lower air pressure creates rolling resistance and decreases gas mileage. You would probably get better mpg's by over-inflating your tires, but tire life would suffer