01.
Tetra-ethyl lead
To improve the anti-knock characteristics of avgas, tetra-ethyl lead is added. There has been pressure to phase this additive out, due to concerns about lead emissions, however, there is currently no alternative that’s safe to use. Shell is working on finding a solution to remove lead from aviation fuels.
02.
Antioxidants (gum inhibitors)
These kinds of additives must be used in avgas to prevent the formation of gum and other antioxidation products. Antioxidants (gum inhibitors) can also be used in jet fuels, however, they are considered more stable than avgas.
03.
Metal deactivator
This kind of additive may be included to improve the thermal stability of fuels. It has been designed to mitigate the effects of dissolved trace metals, especially copper, which can impair the thermal stability of jet fuels.
04.
Corrosion inhibitors
With rust being a potential concern for military and civil aircraft, corrosion inhibitors can be used to reduce weathering in the fuel system. They also improve the lubricating properties of jet fuels.
05.
Fuel system icing inhibitors
These additives reduce the freezing point of any water that may be in the fuel system and prevent ice crystal formation that could restrict fuel flow.
They are mandatory in military jets but are not used in civil aircraft that have fuel heaters. They may be added to either jet fuel or avgas during the fuelling of small aircraft.
06.
Static dissipater additives
These additives minimise the hazardous effects of static charges that build up during movement of jet fuels. They are sometimes used in avgas as well.
