I see your in Idaho, are you guys running winter diesel already? MPG tends to drop on winter diesel since it has a lower energy density than summer diesel, thus you must burn more for the same power. May not explain the 5 month trend but it might explain any recent drops. Otherwise there are so many factors that impact mileage it would be nearly impossible to cover them all.Been leveled with roughly the same size tires, run opti summer and the same gas station the whole time. I thought the new thermostats would help now that I’m running at temp.