I'm sure there are many reasons, but I expect worse fuel economy in the winter. Winter tires are less efficient. Winter diesel is supposedly less efficient -

I'm sure there are many reasons, but I expect worse fuel economy in the winter. Winter tires are less efficient. Winter diesel is supposedly less efficient - gasoline I believe also changes formulas in the winter in some places. Does a warm car run more efficiently than a cold car? I think so, and mine takes many minutes to get up to operating temperature. On a short trip, I may never get there.