FOCUSED ON THE FUTURE OF AVGAS Phillips 66 & Afton Chemical Team Up To Tackle Piston Aviation’s Biggest Challenge

by Ed Leineweber
Published in Midwest Flyer – December 2018/January 2019 issue

For decades, Phillips 66 and Ethyl Corporation have been doing their part to provide the highest quality 100LL aviation gasoline to the piston aviation industry. Phillips 66 and Afton Chemical, sister company to Ethyl, have teamed up to develop an unleaded Grade 100 octane aviation gasoline, UL100, that replaces 100LL and will meet future industry needs. I attended their EAA AirVenture Oshkosh forum in July 2018 and learned more about the details of their efforts and plans.

The Phillips team’s first steps were to envision a UL100 that will be fully compatible with both the present 100LL and the existing avgas distribution network. They see a future aviation fuel that would (1) service the entire fleet of general aviation piston aircraft; (2) meet or exceed the performance and quality characteristics of 100LL as specified in the ASTM D910 standard; (3) produce less hazardous engine emissions compared to 100LL; and (4) minimize any cost increases. Team members believe that their emerging UL100 fuel will meet or exceed these benchmarks.

The primary difference between the current 100LL fuel and the Phillips 66 UL100 under development lies in the additive package. While the petroleum components of both fuels are the same, a new manganese-based package replaces the existing lead-based package found in 100LL. Included in the new Phillips package is a proprietary scavenger formulation and an antioxidant. The relative percentage of petroleum components compared to 100LL have been adjusted to optimize performance with the new Phillips additive package.

As experience over recent decades has demonstrated, there are many challenges in developing a new piston aviation fuel. These include the need for the new fuel to fully satisfy the entire piston-powered fleet in order to simplify the distribution and storage systems; making sure that these distribution and storage systems are in place, with whatever modifications from the current structure are needed; and securing from the FAA fleet-wide authorization for use in piston engines. Until these challenges have been met, the goal of practical, commercially viable lead-free avgas will remain unachieved.

As part of its program to develop and launch UL100 into the market, the Phillips/Afton team is participating in the Piston Aviation Fuel Initiative (PAFI) Unleaded Avgas Development Group working to ensure a successful development of any new unleaded avgas product. This is a broad working group made up of teams of relevant and interested players from government and industry.

Since research and development of Phillips UL100 is still underway, predicting when the finished product will be available is speculative at best. Still the company is targeting commercial introduction in 2021 or the following year.

Many questions surround the Phillips/Afton effort, and some of them were addressed at the AirVenture forum presentation. For instance, it is not certain that Phillips will actually manufacture UL100 if it is approved, but might license production to others. Since Phillips 66 has the most extensive fuel distribution system in the industry, it is likely that it will be heavily involved in whatever approved formulation of lead-free avgas is finally successful in the marketplace. Further, it is unlikely that ultimately more than one such approved formulation will emerge as the 100LL replacement since standardization across the piston engine universe will probably be compelled by commercial realities.

The Phillips/Afton forum presenters stressed that the goal of UL100 development includes the objectives of having their fuel meet the demands of all piston aviation engines, including high-output powerplants, without engine modifications, and without changes in service intervals or aircraft operational practices or procedures. Finally, Phillips/Afton is focused on producing a 100LL replacement that minimizes health and safety concerns, taking into consideration fuel and additive handling and engine emissions.

As detailed in the forum presentation, the active ingredient in the new manganese-based additive package is a chemical known as Methylcyclopentadienyl Tricarbony (mmt®), a metallic octane-boosting additive that was invented in the late 1950s by Ethyl Corporation. This additive is known to provide engine benefits such as octane number increase, detonation protection, valve seat recession protection, and combustion improvement.

According to Phillips/Afton, manganese is an essential element to the body and is naturally occurring in the environment, abundant in soil, the food we eat, the water we drink and the air we breathe. While there are circumstances in which manganese exposure can be health-threatening, initial assessments confirm Phillips’ expectation that “the tiny amounts of manganese used in UL100 would not meaningfully increase the amounts of manganese present in the air.” Further testing and analysis will be undertaken to confirm these initial assessments.

The challenge of replacing 100LL with a commercially- and technically-viable lead-free piston engine fuel has eluded us for many years, but through the efforts of Phillips/Afton, its competitors and the collaborative work of industry, aircraft operators and government stakeholders, we might finally be on the brink of success. Let’s all hope so.

EDITOR’S NOTE: Ed Leineweber is an aviation lawyer, CFII and retired circuit court judge. These days he devotes much of his time to the development of the LoCamp kit aircraft through his company, Golden Age Aeroworks, LLC. He can be reached at or (608) 604-6515.

DISCLAIMER: The information contained in this column is the expressed opinion of the author only, and readers are advised to seek the advice of others, and refer to aircraft owner manuals, manufacturer recommendations, the Federal Aviation Regulations, FAA Aeronautical Information Manual and instructional materials for guidance on aeronautical matters.

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