George Braly, co-founder and chief engineer of General Aviation Modifications Inc. (GAMI), used his annual appearance at EAA AirVenture Oshkosh to update the general aviation community on the status of G100UL, the unleaded 100-octane avgas his company developed as a drop-in replacement for 100LL. GAMI's fuel received FAA approval via a supplemental type certificate covering essentially the entire piston fleet in 2022, a milestone that made it the first unleaded avgas cleared for use across virtually all spark-ignition aircraft engines and airframes rather than a subset limited to lower-compression powerplants. Since that approval, GAMI has been working through the slower, more complicated phase of the project: building out distribution infrastructure, securing fuel terminal and refinery partnerships, and getting G100UL physically available at airports rather than just legally authorized for use.
For working pilots, particularly those flying high-performance piston singles and twins, turboprops with piston-powered support fleets, and flight schools and FBOs that depend on 100LL, this update matters because the timeline for eliminating leaded fuel keeps moving. The FAA and industry stakeholders committed to the EAGLE initiative (Eliminate Aviation Gasoline Lead Emissions) with a target of removing lead from avgas by the end of 2030, and environmental and legal pressure has been building faster than that voluntary timeline in some regions. California in particular has seen airport-level leaded fuel bans and litigation tied to lead emissions near general aviation airports, most notably around Reid-Hillview and Santa Clara County facilities, which pushed some of the earliest real-world G100UL deployments. Pilots operating in or near these markets have had to pay close attention to which FBOs carry which fuel, whether their aircraft and engine combination is covered under the GAMI STC, and how mixed-fuel operations and record-keeping requirements affect maintenance and insurance considerations.
Braly's GAMI has also faced friction from competing approaches, most notably Swift Fuel's UL94 product and the broader ASTM D7547 unleaded avgas standard effort, which some engine and airframe manufacturers have preferred as an industry-consensus alternative to a proprietary single-source fuel. That competitive and standards-setting dynamic is part of why updates from Braly at high-visibility events like AirVenture carry weight: they signal not just technical progress but the commercial and political trajectory of which fuel, or fuels, will actually reach the pump at scale. Distribution economics, refinery capacity, terminal blending logistics, and cost parity with 100LL remain the practical bottlenecks separating a certified fuel from one pilots can reliably purchase at their home airport.
Broadly, the unleaded avgas transition sits alongside other structural shifts reshaping piston GA, including rising 100LL prices, aging fleet demographics, and parallel efforts around electric and hybrid propulsion for training aircraft. For flight departments, FBOs, and individual owners, the practical takeaway is that the shift away from leaded fuel is no longer a distant regulatory abstraction but an operational planning issue: fuel availability by airport, STC compliance documentation, and potential future restrictions on 100LL sales are all variables that need to be tracked now rather than after a mandate arrives. Continued visibility for GAMI's progress at events like AirVenture gives operators an annual checkpoint for gauging how close the industry actually is to a fully unleaded piston fuel supply chain.