ABOVE: The FAA and Environmental Protection Agency (EPA) share concerns about lead emissions

 US energy company Philips 66 is to suspend testing of its 100M unleaded aviation fuel, the Federal Aviation Administration (FAA) has confirmed, citing ‘issues encountered with durability testing’.

“We can confirm that PAFI evaluation has been paused on the Phillips 66/Afton Chemical 100M unleaded fuel,” Philips 66 told Pilot. It added that the company remained “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 fuel was being developed (in conjunction with partner Afton Chemical) as part of the Piston Engine Aviation Fuels Initiative (PAFI) as a drop-in alternative to 100LL avgas. As of August 2022, two candidate 100 octane unleaded fuels were in development; the other project in the hands of Lyondell / VP Racing.

The PAFI programme was first established in 2014 to ‘remove lead from avgas without adversely impacting the safe and efficient operstion of the existing GA fleet,’ explained the FAA, who concluded that ‘although no high-octane unleaded replacement fuel has yet been qualified under PAFI as a suitable drop-in candidate, approval of a qualified fuel would occur following the issuance of a new production specification / standard of safety and reliability’.

Afton Chemical have not yet responded for comment.