Phillips 66 Suspends Unleaded Avgas Testing

Phillips 66 has "paused" evaluation of its unleaded avgas alternative after what sources have told AVweb was a major test failure. Phillips 66 confirmed to AVweb that evaluation of the fuel it is developing with Afton Chemicals through the Piston Engine Aviation Fuels Initiative has been suspended, at least temporarily. "We can confirm that PAFI evaluation has been paused on the Phillips 66/Afton Chemical 100M unleaded fuel," the oil giant said in a statement to AVweb. "Phillips 66 is committed to its vision of developing an unleaded aviation fuel offering and is currently evaluating this product’s development and all viable alternative options."

The FAA also confirmed that "PAFI evaluation of the Phillips 66/Afton Chemical 100M unleaded fuel has been paused due to issues encountered during durability testing." It did not elaborate on the nature of the durability issues. According to sources with direct knowledge of the issue, the Phillips/Afton fuel was powering a Lycoming engine in a test cell on a 150-hour endurance test and the engine failed due to a buildup of manganese deposits that fouled the spark plugs and/or caused pre-ignition. Phillips did not confirm that as the cause of the evaluation pause.

The departure of the Phillips/Afton entry leaves three contenders in the unleaded avgas evaluation. LyondellBasell/VP Racing Fuels is also going through the PAFI process, which involves the evaluation of the fuel by the FAA with the goal of earning "fleet authorization" as a universally acceptable fuel for spark ignition piston engines. Swift Fuels is seeking Supplemental Type Certificate (STC) approval for its 100R fuel and General Aviation Modifications Inc. has already received STC approval for its G100UL fuel for virtually all gasoline engines currently in use by aircraft in the U.S. To use the GAMI (and eventually the Swift) fuel, individual operators must obtain the STC for the aircraft that will use the fuel. There is some paperwork involved and a nominal fee to get the STC and install a placard. The GAMI fuel has been in limited use for more than a year.