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Understanding the evolving requirements of Avgas

Release date:
May 2022
Michael Rodda s1
Dr Alisdair Clark, Air bp’s aviation fuels research and development manager, explores the opportunities for unleaded Avgas. 


When you purchase Avgas for your aircraft you are buying a special fuel benefiting from more than 100 years of history that has improved the reliability and safety of spark ignition piston engine flight. 


Originally Avgas was unleaded, but with the discovery of the performance increasing additive tetraethyl lead, the world transitioned to the leaded high octane ‘100’ grades which dominate the market today. According to the FAA, Avgas 100LL is the most commonly used grade with 190,000 registered piston-engine aircraft in the US operating on this product1


Times are changing however and the aviation industry aspires to move away from the use of leaded Avgas for environmental reasons and to ensure the replacements can also support the industry’s net-zero carbon aims. A recent study in the US by the National Academies of Sciences, Engineering and Medicine2 has highlighted the benefits of such a change together with a range of options to achieve this objective. This has prompted the US general aviation industry to set a 2030 deadline to phase-out 100LL and associated leaded grades3. The EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative, which was announced on 23 February 2022, aims to bring together government and industry to safely eliminate leaded aviation fuel without adversely affecting the existing piston-engine fleet. Given a similar European focus on lead emissions from ECHA (the European Chemical Agency), other regions across the globe are expected to follow suit. 


What does this mean for Avgas customers?    

Well, in the modern world a range of options are available for light aircraft – classic Avgas engines, compression ignition engines and even electric. Each has benefits / limitations with light-weight Avgas units still offering a reliability, range and payload ability which is hard to beat. 


Air bp has been following developments closely and already has an industry approved mid-octane unleaded Avgas grade, UL91, to support this market transition. While not appropriate for all aircraft, this grade does offer the same high energy content as traditional 100LL (43.5 MJ/kg minimum). Approval for a sustainable low carbon manufacturing route for the major constituent, iso-octane, is also being discussed by the industry.


Whether there will be a drop-in replacement grade for 100LL is still open to debate – some specialist fuels have been manufactured, however the joint FAA-industry Piston Aviation Fuel Initiative (PAFI) programme is still in progress. Technical requirements for such a fuel are high and with 100 years of knowledge there is little room for compromise. Such commitment from the industry is significant and comparable to the good work to develop  sustainable aviation fuel (SAF) for the global turbine fleet. The aim, as always, is to allow the aviator to fly safely and efficiently whichever engine technology is in use.


Looking to compression ignition aviation engines, these tend to favour Jet A or Jet A-1, both already available from Air bp. Both products offer the quality control expected for flight operations, similar to Avgas, combined with a low freeze point / appropriate viscosity for use.  


As for the advancement of electric aircraft - a further alternative where payload/ range is less critical - the wider bp group brings extensive experience in this area in terms of rapid charging as part of automotive technology. 


When 2030 arrives, just as in the previous 100 years, Air bp will continue to seek to meet your fuel requirements, be it a 100LL replacement grade, UL91 Avgas, Jet A/A-1 for a compression ignition engine or a fast electrical charge. 


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