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UL Fuel FAQ
Disclaimer: Although the City of Middleton and Middleton Municipal Airport are committed to the conversion to a universally accepted unleaded aviation fuel at the airport, the process and distribution of unleaded fuel is governed by the Federal Aviation Administration and the aviation fuel manufacturers, respectively. The input of aviation engine manufacturers is also a necessary component of the process as well. The timeline for conversion is outside of the control of local airports. For more information on what steps the City of Middleton and the Middleton Municipal Airport have taken in the interim, please view the FAQs below. For current information and recent developments on the Federal Aviation Administration's (FAA) Eliminate Aviation Gasoline Lead Emissions (EAGLE) Initiative, please click here.
In June 2025, the FAA put out notice to all airports that existing grant assurance (Grant Assurance 40) specifies that if 100-octane low lead aviation gasoline (100LL) was available at an airport at any time during 2022, the airport owner or operator cannot restrict or prohibit the sale or self-fueling of 100LL for use by general aviation aircraft operators until certain criteria are fulfilled. As of now, the FAA Administrator has not authorized a replacement fuel for 100LL for aircraft, including rotocraft, that meet the criteria set forth in Section 770 of the FAA Reauthorization Act of 2024 (47107(22)(B)(i) and (ii)). The FAA will provide additional information when the criteria are met. https://www.faa.gov/airports/airport_compliance/compliance_guidance/Grant-Assurance-40-Leaded-Aviation-Gas-QA.pdf.
The FAA has put out a request for comment on its draft plan for transition to unleaded aviation fuel, which is open until March 13, 2026 for comment. To provide comment, please click here: https://www.federalregister.gov/documents/2026/01/12/2026-00296/draft-faa-transition-plan-to-unleaded-aviation-gasoline. A copy of the FAA's Draft Plan for Transition to Unleaded Aviation Gasoline can be found here.
Yes, the airport has to infrastructure to offer 94UL fuel, which we started offering in 2023. However, we were not able to offer 94UL fuel for a period of time due to the change in price from the distributor. We have now secured another shipment of the 94UL fuel at a more reasonable price, and will offer it for sale again.
Unleaded 94UL is a type of aviation fuel designed for piston aircraft engines. It is formulated without lead additives, making it a more environmentally friendly alternative to 100LL fuel.
Unleaded 94UL is important for environmental reasons because it does not contain lead. The EPA noted in their 2023 endangerment finding that 100LL aviation fuels can contribute to air pollution. Switching to unleaded fuel helps reduce or eliminate the environmental impact.
By eliminating the lead additive, Unleaded 94UL reduces the emission of lead particles into the atmosphere during aircraft operation. This contributes to lower environmental impact and improved air quality.
Many aircraft in the current general aviation fleet require 100-octane fuel to avoid engine detonation, which can lead to catastrophic engine failure and an unsafe flying environment. Lead has long been used as the only additive to boost fuel octane, allowing piston engine-powered aircraft to fly safely. Finding a suitable unleaded substitute has long been a goal of the general aviation industry and the Federal Aviation Agency (FAA).
Unleaded 94UL is specifically designed to be compatible with most piston-engine aircraft. More than 70% of the general aviation fleet is compatible with 94UL fuel.
The cost of Unleaded 94UL may vary, and it is influenced by factors such as production costs and market demand; however, in our local market, prices are comparable to other fuels.
The FAA has authorized some initial testing of 100UL, a 100-octane unleaded aviation fuel that would be acceptable for all aircraft types. When this product is ready for mass production and widespread distribution, it is expected to fully replace traditional aviation fuel. The City of Middleton remains committed to working with fuel suppliers and aircraft owners to make this transition seamless and effective.
On October 18, 2023, the U.S. Environmental Protection Agency (EPA) announced its final determination, after a multi-year study, that emissions of lead from aircraft that operate on leaded aviation fuel cause or contribute to air pollution which may reasonably be anticipated to endanger public health and welfare under the Clean Air Act.[1] By way of this finding, the EPA is now obligated under the Clean Air Act to propose and circulate regulatory standards for lead emissions from certain aircraft engines. The Federal Aviation Administration (FAA) must also “develop standards that address the composition, chemical, or physical properties of an aircraft fuel or fuel additive to control or eliminate aircraft lead emissions.”[2] The EPA’s endangerment finding does not ban or impose restrictions on the sale or distribution of existing leaded aviation fuel, 100 low-lead (100LL).[3] The transition to 100-octane unleaded aviation fuel has been mandated by the FAA and is scheduled by the FAA to happen by 2030.
[1] U.S. Environmental Protection Agency. (2023, October 18). EPA Determines that Lead Emissions from Aircraft Engines Cause of Contribute to Air Pollution [Press release]. https://www.epa.gov/newsreleases/epa-determines-lead-emissions-aircraft-engines-cause-or-contribute-air-pollution
[2] U.S. Environmental Protection Agency, 2023.
[3] U.S. Environmental Protection Agency, 2023.
In 2022, the general aviation industry associations, the American Petroleum Institute, and the FAA established the Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative with the goal of eliminating leaded aviation fuels in piston-engine aircraft safely by the end of 2030. Through this initiative, three (3) high octane unleaded fuels are in the testing, approval and commercialization process. As soon as the FAA has approved a 100UL fuel for fleetwide distribution and it is commercially available and distributed in quantity to our regional distribution channel, the Middleton Municipal Airport will proceed to secure it for use at the Airport and phase out the use of 100LL fuel.
The FAA has put out is draft transition plan to unleaded aviation fuel for public comment. To see a draft of the plan, please click here.