The decades-long effort to find a suitable replacement for 100-octane leaded avgas moved one step closer to a solution on July 27 when General Aviation Modifications Inc. (GAMI) announced that it has received two supplemental type certificates authorizing the use of its G100UL high-octane unleaded avgas. One STC covers a limited number of models of Lycoming engines and the second is for a limited number of Cessna airframes.