The REAL reason your fuel economy collapses in the winter

of course from il to cheyenne it is all uphill
in Des Moines it is 1000 feet above sea level
Cheyenne is 6000 feet
predominant NW wind
i get .5 to .8 better fuel economy headed east then west

Cheyenne to Evanston just let it rip nothing makes mileage worse or better

 

Snowwy wasn't really wrong. The density altitude (how high the airplane thinks it is) is much lower in the winter, giving planes far greater climb performance in winter vs. summer. It's not uncommon at the higher elevation airports for pilots to find themselves over Max Takeoff Weight because the density altitude has gone through the roof on a very hot day.

And while it doesn't effect most flights, biz jets that go for the really high FL's can get a bit higher sooner than in the summer, and the far rarer planes such as the SR-71 and U-2 that intentionally operated on the far edges of their performance envelopes did indeed fly higher in cooler air temperatures.


And it's the combination factors, as pointed out up ^ there, that affect winter fuel mileage. IIRC, the increase aero drag and reduced intake temp (more power) offset each other fairly equally, it's the lower density winter fuel and the higher parasitic drag of the colder tires, gears, and bearings that drag economy down. And in much of the country, the wind does blow harder in the winter, too.

 

In minus 25c my diffs will run at 110 to 120f on dry roads.. Yet at 0c/32f on slightly wet/slushy roads gauge doesn't move enough to register and you can see by boost gauge it's harder to pull load

 

For me its keeping the idle at 10,000. Spring summer and fall, I shut the truck off any chance I get. I don't have an APU.