I have been cautious to avoid commuting under 5°F because the manual said that is the minimum operating temperature, but I recently reached out to a Pinion technician who said the main consideration with temperature is the gearbox becoming pressurized when you bring it back inside from extreme cold. Nothing operationally will damage the gearbox in temperatures below 0, but because the gearbox is completely sealed, a rapid increase in temperature can cause pressure to build inside the gearbox. The pressure won’t hurt the gearbox but can push some oil past the seals causing a temporary oil leak. In that case put a sheet of cardboard under it in the winter then change the oil every spring to make sure it’s still topped up.