Mpg drop isx15

[Hammerhead]

The biggest energy content factor in summer fuel is paraffin wax. Just like a candle, the wax slows the burn rate and increases the burn temperature, thus creating more heat expansion energy. The wax content needs to be scaled back, or removed completely in colder climates, to keep the fuel from gelling. If you removed the tell from gelled fuel and analyzed it, you'd find its almost pure paraffin wax.
Winter fuel burns quicker and cooler...add to that colder more dense air and AFR isn't nearly as optimal. This is why I remapped my turbo for winter trying to control the efficiency losses.
Add in that the colder air is more dense and your aerodynamic efficiency is reduced because it's harder to push the air out of the way, and the Aero Drag vacuum at the back of the trailer is increased because of this same density creating a stronger vacuum.
Colder ambient temps also means your tires do not expand as much either, therefore creating a larger surface contact area, once again increasing drag.
The colder temps also means the rolling hubs (trailer & steering) are a lot cooler so the oil doesn't flow as freely causing wheel bearing resistance...god forbid you have grease hubs and you increase that even more!

If you own your trailer, changing hub oils to synthetic oil will pay for itself over and over again!

Ain't winter fun?