Question : Does cold weather affect car fuel consumption?
Answer : Yes !! It most certainly does. Cold air is more dense so the aerodynamic drag of pushing the vehicle through the air is higher than when pushing through hot air. Also it requires more fuel to warm the engine to normal operating condition as it has to run rich (choke) for a longer period of time.
Also in cold weather engine oil is thicker, transmission and axle oil are also thicker so it requires more power to pump the oils and move the gears. Colder tires also don't roll as easily as warm tires.