Except... certification is done: https://www.aopa.org/news-and-media/all-news/2022/september/01/closer-to-an-unleaded-future https://www.aopa.org/news-and-media

Except... certification is done: https://www.aopa.org/news-and-media/all-news/2022/september/01/closer-to-an-unleaded-future https://www.aopa.org/news-and-media/all-news/2022/september/... > The FAA signed on September 1 supplemental type certificates that allow General Aviation Modifications Inc.’s 100-octane unleaded fuel (G100UL) to be used in every general aviation spark-ignition engine and every airframe powered by those engines. All piston engines and aircraft are certified for G100UL.