Well, I can say that ICE car have a variance. Just plenty of folks don't care. Using the receipts every time I pumped gas in my 2010 Honda Fit Sport for a few years, I could see that during hot summers and winter (maybe even cold late fall/early spring) the MPG was always lower than when there are moderate temperatures.
The hot summers is because the engine has to work a little bit harder to power the AC system. Cold weather has influences on running conditions. Some say it’s denser air causing more resistance to the airflow, blah blah blah. It should be sufficient to say, there’s an effect in winter.
Don’t have to take my word for it…
Fuel Economy in Cold Weather.
There was more I typed, but it might be off topic, so I’ll leave it out.