Winter diesel (also called winterized diesel or #1 diesel) is diesel fuel blended or treated for cold weather operation. Refiners may blend #1 diesel (kerosene) with #2 diesel to lower the cloud point, or add anti-gel additives at the terminal. However, retail winter blends often don't provide sufficient protection for extreme cold. Fleet operators in northern climates typically add supplemental anti-gel additives like Fuel Ox Cold Charge for reliable cold weather protection.