Testing of UL100E under the FAA’s Piston Aircraft Fuel Initiative (PAFI) is expected to conclude by September 2026, according to VP Racing Fuels, as the unleaded aviation gasoline continues to move through engine, aircraft, and FAA Technical Center evaluations.
UL100E, co-developed with LyondellBasell, is the final test fuel remaining in the PAFI program and remains under review across a range of platforms as the FAA works toward potential fleet authorization.
The testing effort follows ASTM International’s publication in November of ASTM D8631-25, the first standard specification for unleaded aviation gasoline test fuel containing ethers. The specification provides an industry-recognized framework allowing PAFI evaluations to continue with an established focus on safety, performance and compatibility with the existing fleet. PAFI is a collaborative FAA-led program involving aircraft and engine manufacturers, fuel developers and industry stakeholders.
The Aircraft Owners and Pilots Association (AOPA) said the ASTM specification represents an important step in the broader transition away from leaded avgas.
“This is a meaningful milestone as the aviation industry continues to make progress toward an unleaded future,” said AOPA President and CEO Darren Pleasance. “We congratulate VP Racing and LyondellBasell for the work they’ve done and for contributing to the momentum needed to deliver safe and reliable solutions for general aviation.”
AOPA added that results from UL100E testing are expected to inform future FAA decisions on eligible aircraft, operational considerations and any required engine modifications, as the association continues working toward a goal of transitioning to unleaded avgas by the end of 2030 in the continental United States and 2032 in Alaska.
