To continue with the public service message, colder air is much more dense and therefore, with the H2 being as aero as a brick, it takes more power to push through.
PLUS, they add some **** to gas in the winter, who knows what that does.
ummm.........let's see........ well, it's colder so the grease and oil is less efficient at reducing friction.
ok...ok.... you have more clothes on in the winter and that adds extra weight.
one more.....hmmm..... well..... the days are shorter and you use your lights more which draws more energy from the alternator which in turn takes more fuel.
