What is the “cloud point” of diesel fuel and why is it important to filtration?
#2 diesel fuel has a wax component that contributes to the lubricity and heat value of the fuel. The “cloud point” refers to the temperature when the wax precipitates out of the fuel in the form of small wax crystals. Different fuel blends can have very different cloud point temperatures, generally ranging from -10°F to +40°F. #1 diesel fuel does not contain large amounts of wax, and therefore does not have a noticeable cloud point. Diesel fuel distributors blend local diesel fuel supplies so that the cloud point is usually not reached. However, if ambient temperatures fall below the cloud point of the fuel on a vehicle, the precipitated wax crystals can quickly coat and plug a filter element. To avoid filter wax plugging and loss of engine power, diesel fuel filter systems are often supplied with an auxiliary fuel heating or return fuel heat recovery systems. Fuel additives are also available that modify the formation of wax crystals, making them less likely to plug the filter.
