G100UL Avgas has already been rigorously tested to the FAA’s highest standards. Lycoming and Continental have both tested G100UL and found no deficiencies. Nor have they pointed out any to GAMI.
In recognition of this, Lycoming should revise its Service Instruction #1070AB dated 04-08-2020, and Continental should petition the FAA for changes to its engine Type Certificates to indicate the optional G100UL. Otherwise, the GAMI STC is still an “alteration” to a type design.