At low ambient temperatures, the fluidity of diesel fuel decreases due to the crystallization of the paraffin contained in it. Diesel fuel gets thick like honey. In this regard, oil refineries add additives to diesel fuel intended for use in winter, which improve the fluidity of the fuel and allow the engine to start up to a temperature of -15°C (or down to -22°C respectively when using Super Diesel fuel).
However, these additives are not always enough to ensure the perfect operation of the engine, so the fuel filter is equipped with an electric heater. This prevents crystallization of the diesel fuel even at extremely low ambient temperatures.