seasonal variations in fuel consumption

[supton]

My TDi didn't seem to suffer in winter, not greatly anyhow. But it would be driven for close to an hour at a time, thus warmup time was minimized. [Plus it wouldn't warm up at idle thus I rarely did that.]

My gassers, they seem to fire up and go right to high idle, presumably to get heat into those cats. My truck takes a big whammy, lots of gear oil to warm up. [I saw that the 2019 Rams are running coolant to at least the rear diff. Link]

 

[CR94]

Originally Posted by bobdoo
... The increase in oxygen content due to higher air pressure has no effect. You run a smaller throttle under those conditions. ...
Not exactly. Even if the load on the engine were the same (which it isn't, because of other factors like air resistance), the smaller throttle opening would result in greater throttling losses.

That's only one cause of higher fuel consumption in cold weather that I haven't seen mentioned yet. Another is greater hysteresis losses in tires, even if the pressure were the same---which it typically isn't.

 

[DGXR]

For me (in Sacramento, CA), the biggest factor is warm-up time. In winter, my engines spend much more time in open loop operation, which gobbles up gasoline. The difference in warm-up time is really shocking. When the summer nights only get down to 75F, my engine can reach full temp in 3-4 minutes. Winter nights sometimes get down to 28F and it can take 7-8 minutes to reach full temp. I usually warm up my engines the same way but give them an extra 30 seconds idle time if it is very cold.
("Very cold" lol what a joke, I feel sorry for you in the Dakotas and midwest... hang in there.)
Also I'm pretty sure the fuel here has 10% ethanol year-round. But people in Sacramento drive VERY stupid and wet roads can induce speeding in some and panic in others. So there are more accidents during the winter, but I don't think that can be considered a reliable seasonal factor.
Edit: I just did some quick math and my seasonal MPG variation is about 10% (~25 summer, ~22 winter).

 

[Andrew1972]

2018 Tiguan went from 29 MPG summer to 26.5 MPG average winter. I think the start stop does not trigger as much with colder weather. Also my wife idled vehicle sometimes for 5 mins in winter.

 

[Garak]

That's my biggest hit to fuel economy in winter, I'd wager - idling. Right now it's -27 C. I will decidedly not be running it for 30 seconds and driving away.

 

[Uphill_Both_Ways]

Yesterday in the depths of the deep freeze I got an indicated 6.6/100 kms on my regular 70 km/h run of 40 to 45 kms one way. In summer I get 5.6 to 5.7.

 

[Garak]

Driving through Saskatoon's unplowed streets are always so helpful for fuel economy, too!