NATA Recognizes Publication of ASTM D8631-25 as Important Step in UL100E Evaluation Process

NATA (the National Air Transportation Association) congratulates LyondellBasell and VP Racing on an important milestone marked by the publication of ASTM D8631-25, the Standard Specification for Unleaded Aviation Gasoline Test Fuel Containing Ethers. Issued by ASTM International in November, the standard establishes the first ASTM specification for UL100E, the unleaded aviation gasoline co-developed by LyondellBasell and VP Racing. UL100E is currently undergoing evaluation by the Federal Aviation Administration (FAA), in coordination with aircraft and engine manufacturers, through the FAA’s Piston Aviation Fuels Initiative (PAFI), with completion of testing anticipated by September 2026.

“The publication of ASTM D8631-25 reflects meaningful progress for UL100E and the broader effort toward a commercially viable unleaded aviation fuel, affirming the extensive technical work led by LyondellBasell and its partners,” said NATA President and CEO Curt Castagna. “An ASTM standard specification is a prerequisite for a fuel to advance through evaluation and consideration under the FAA’s Piston Aviation Fuels Initiative. As progress toward an unleaded aviation future continues, NATA reaffirms its support for clear, structured, ASTM-based processes that advance innovation while reinforcing safety and operational certainty.”

PAFI is overseen by a collaborative industry/government group of technical experts and evaluates multiple characteristics of candidate fuels, including but not limited to detonation, durability, performance, and materials compatibility. PAFI testing data and results are also shared with engine and airframe original equipment manufacturers (OEMs) to provide confidence in the use of the new fuel; this data is used to support the fuel’s ASTM production specification.

NATA will continue to support its members and the aviation community by providing resources, education, and advocacy to facilitate a smooth and safe transition to unleaded avgas as a leader on the joint FAA/industry EAGLE (Eliminate Aviation Gasoline Lead Emissions) Initiative. For more information on the transition to an unleaded aviation fuel and EAGLE, visit flyeagle.org.  Visit NATA’s unleaded aviation fuel advocacy page for additional information and resources.