FAA requests unleaded fuel pireps

Special Airworthiness Information Bulletin 2025-04 issued March 28 seeks reports of service difficulties or abnormal maintenance issues related to the use of unleaded fuel, the agency wrote. "The FAA is also interested in hearing from operators who have transitioned to unleaded fuel without issue."

The FAA notes there are "several" unleaded fuels currently available, "and additional fuels are likely to be available soon." The arrival of these fuels prompted legal and administrative efforts to force the displacement of 100LL from various California airports, resisted by aircraft owners concerned about the safety of unleaded fuels. The FAA issued a long-awaited ruling in March, ordering Santa Clara County to reverse its 2022 ban on 100LL at two county airports, agreeing with AOPA's argument that the ban, and related moves by the county, violated various federal grant assurances.

The Eliminate Aviation Gasoline Lead Emissions (EAGLE) government-industry coalition (of which AOPA is a founding member) seeks to transition to lead-free fuels for piston aircraft "without adversely impacting the safe and efficient operation of the existing general aviation (GA) fleet," the agency wrote in the SAIB.

AOPA President Darren Pleasance reiterated in January that the association continues to "tirelessly advocate on behalf of all our members, and the general aviation industry more broadly, for a transparent approach to getting safely to the unleaded future we're all committed to."

Pleasance wrote that a key component of that effort is a "rapid and transparent assessment by both the FAA and fuel producers" to determine if reported problems (including leaks, which AOPA experienced firsthand) are, in fact, related to the use of a new fuel. "We owe it to the entire industry to quickly assess issues as they arise and respond accordingly as we learn. AOPA will also continue to partner with all key stakeholders across the aviation ecosystem to advocate for open and transparent materials compatibility testing throughout the supply chain."

On the legal front, a California judge heard arguments March 5 on his preliminary ruling that would preserve 100LL availability at nearly two dozen airports in the state. A final ruling is still pending in the case, which prompted industry stakeholders including the General Aviation Manufacturers Association to argue that G100UL, produced by General Aviation Modifications Inc. and approved by supplemental type certificate, remains, "the only aviation fuel that has not been subject to a stakeholder consensus peer review process."

GAMA also noted that G100UL is not yet approved by the FAA for piston helicopters.

AOPA reported in detail on a yearlong demonstration of G100UL, running the new fuel in one engine of a Beechcraft Baron and avgas in the other engine. While engine data analysis suggested that G100UL has some advantages over 100LL, including increased power running lean of peak, AOPA also observed the fuel's tendency to stain paint. Leaks in both tanks were also observed, likely related to the age and installation of the fuel bladders.

The FAA seeks detailed reports, including aircraft and engine make and model, which fuel was used, how much was used, and additional information. AOPA asks members who email their experience reports to the FAA as the SAIB requests to also share a copy of the contents with AOPA using this brief form.