Small displacement engines work very hard in cold weather.
The obvious, the fuel mixture is richer, for longer periods of time is only part of it.
The cold tire rolling resistance is very high.....difficult to deform the tread to make a footprint.
Every wheel bearing has high rotational resistance.....that grease in there never really warms.
Motor oil and trans fluid viscosity is high for a longer period of time.
You are running the heater fan, usually the lights, and maybe the heated seats as well as trying to charge a cold battery that is rather resistant to recharging because it is living a cold corner.......so, the alternator is adding to the drag.
So, as you can see, there is quite a conspiracy going on to drive the mileage down.
A large displacement, high torque engine doesn't have much difficulty with all these things dragging at it, so the mileage isn't affected near as much as the 1.4 or any other small displacement, low torque design.
Good news is the mileage improves dramatically once the temperature rises.....something that isn't going to change much with a larger engine.
Rob