Winter diesel fuel additives are used to prevent plugged fuel filters and increase the winter operability of diesel fuel.

How can you prevent a plugged fuel filter?

When properly used, cold filter plugging point (CFPP) additives change the shape and size of wax crystals so they can pass through fuel system filters at lower ambient temperatures than without the use of these additives.

A wax anti-settling additive (WASA) can prevent wax from settling if used in the additive package. WASA additives disperse the treated wax so it stays suspended in the fuel and does not settle on the bottom of the tank. The CFPP temperature is now more reliable due to the WASA component.

A caveat of diesel fuel additives and CFPP treatment: TIME

The longer a treated fuel sits in a “Slow Moving Tank” at low temperatures, the more likely gravity will promote the settling of wax at the bottom of the tank.

The increased wax density overwhelms filters on startup (the fuel pick-up is normally on the bottom of the tank). Fuel filter plugging will occur at a temperature higher than the CFPP temperature.

Testing Methods Fuel Testing is of extreme importance. To evaluate wax settling performance in CFPP additives, a treated and untreated fuel sample is cooled to sub-zero temperatures. The sample sits undisturbed and time-lapse photos are taken.
The resulting photos show the rate at which wax settles and visually indicate the reliability of the given additive at a selected treat rate.

Conclusion It is notable that the additives tested exhibit significant differences in WASA performance. CFPP additives with higher levels of WASA additive visibly indicate the most reliable operability.

When concerned about a critical application, i.e. such as a state DOT bid or another requirement that has a hard CFPP target to meet and penalties associated with non-attainment of the target CFPP, one should look for the additive products that provide the best protection from settling.