As part of PAFI, in June 2013 the FAA requested that fuel producers submit their replacement fuel proposals to the FAA for evaluation. By July 2014, the agency received 17 formulations from six companies and assessed candidate fuels in terms of their impact on the existing fleet, the production and distribution infrastructure, the impact on the environment, toxicology, and the cost of aircraft operations. In September 2014, the FAA accepted four fuel formulations into the PAFI Phase 1 test program. Approximately 167,000 GA aircraft in the U.S. currently rely on 100 octane low-lead aviation gasoline for safe operation.

The small quantity of lead in the fuel creates the high octane levels needed for high-performance aircraft. Most commercial airplanes do not use leaded gas. Visit the FAAs aviation gasoline website to learn more. Phase 1 testing of the four candidate fuels concluded in December 2015. It included basic fit-for-purpose and chemical property laboratory evaluations, six rig tests, materials compatibility testing, engine testing, and a literature study which evaluated the chemical components of the fuels to obtain information on their toxicity and environmental impact.

The companies then used the Phase 1 data to update the feasibility assessments that they submitted with their original proposals to assess the impact of their fuel on the current GA fleet of engines and aircraft, including the number and extent of aircraft modifications. They also examined production and distribution costs and environmental factors. The FAA reviewed the Phase 1 PAFI data and the updated feasibility assessments, and then selected the two fuels which would have the least impact on the GA fleet and on the fuel production and distribution infrastructure.