With a decrease in outside temperature, the fluidity of diesel fuel decreases due to the precipitation of paraffin. Fuel can thicken to a honeydew state and clog the fuel filter. For this reason, mineral oil manufacturers introduce additives into diesel fuel in winter, which increase fluidity and guarantee engine start at temperatures down to -15°C or -22°C (super diesel).
In BMW 3 Series vehicles with a diesel engine, the fuel is additionally heated by a heater located next to the fuel filter.