I’m somewhat lucky that I get to spend a nice portion of my summer in the Midwest, where temps stay kinda pleasant. I actually started not using a/c as a way to acclimatize after moving to Texas from a Mediterranean zone of California. I continued as it aided mpg, and here we are again, I use it as an aid to acclimatize since I spend so much time away. Truck is remarkably consistent. I got lucky with weeks’ worth of light loads, and have had mostly heavy ones of late (40,000lb or more). Native FCD says 8.8mpg, company says 8.4, either way I’d say not too bad.