Policy dictates that the current issue of the fuel specification, Defence Standard (Def Stan) 91-090, for Aviation Gasoline (Avgas) is adhered to.
Avgas 100LL is the staple fuel for most piston engine aircraft and contains the additive tetra-ethyl lead (TEL). TEL is used to boost and maintain the octane level and prevent destructive detonation within engines. High-compression and turbocharged engines are particularly affected by such issues.
The Ministry of Defence is driving to reduce environmental contaminants such as TEL where possible and, as soon as alternatives are proven to be fit for purpose and safe in use, it is our policy to seek clearances from the airframe and engine Original Equipment Manufacturers (OEMs) for their inclusion in the procurement process.