With the onset of the autumn-winter season, diesel car owners often face unpleasant difficulties starting the engine, loss of power or sudden stoppages on the road. The main culprit behind these problems is the paraffin wax crystallisation process – a phenomenon in which paraffin crystals form in cooled fuel and can quickly clog the fuel filter. To prevent such a situation, specialised diesel anti-gel additives are used, whose effectiveness depends directly on adding them in time and using the correct dosage.
Paraffins are a natural part of the composition of diesel fuel. At high temperatures, they remain completely dissolved, but as the temperature drops, they begin to crystallise, causing the fuel to lose its clarity. The temperature at which this process becomes visible is called the cloud point. As temperatures fall further, the crystals grow and cluster together, becoming trapped in the pores of the filter and restricting the flow to the engine, even though the liquid may still appear normal inside the tank. For winter operation, the critical plugging temperature is of key importance, and improving it is the main purpose of an anti-gel additive.
The additive works by limiting the growth and clustering of paraffin crystals into large formations, allowing the fuel to pass freely through the filter elements. It is important to note that the product does not remove the paraffins themselves and does not make the fuel immune to freezing, but serves as a reliable preventive measure.
For the chemistry to work properly, it must be evenly mixed with the diesel before crystallisation has begun. It is generally recommended to add the anti-gel when the temperature of the liquid is slightly above the cloud point – ideally before refuelling at a petrol station, while the fuel is still completely clear. If the car has been left in the cold for a long time and the paraffins have already settled, adding the product to a cold tank will not help, as it does not have defrosting properties.
The effectiveness of the protection depends both on the quality of the seasonal fuel itself and on following the dosing instructions provided by the manufacturer of the respective product. Exceeding the recommended quantities or treating fuel that has already been protected a second time does not lead to any further reduction in the plugging temperature.
In addition to pure anti-gel additives, the market also offers multifunctional products for comprehensive care. They combine low-temperature protection with fuel-system cleaning functions, an increase in the cetane number, improved lubricating properties for injectors and the pump, as well as a demulsifying effect for the effective separation of condensed water. The latter, however, requires regular servicing and cleaning of the vehicle’s water separator, as the additive does not remove the accumulated moisture by itself.
If the fuel has nevertheless become waxy and the filter is blocked, the only correct solution is to safely warm the vehicle in an enclosed heated space and inspect the fuel component. Anti-gel additives themselves should also be stored under suitable conditions and protected from freezing – if they thicken due to the cold, the bottle should be allowed to acclimatise to room temperature and shaken vigorously before use so that it can regain its full functionality.