The FAA has. awarded GAMI an STC for 100 unleaded. Their initial AML list is primarily the aircraft in the Embry Riddle fleet, but they claim it will be expanded quickly. They also say it is easy to produce, AVFuels will be an initial producer, it will be 60 to 90 cents more per gallon. Per the STC is is totally mixable at any ratio with 100LL making switch over in bulk tanks easy.  Here is George Braly and Tim Roehl explaining the product.  https://www.avweb.com/multimedia/airventure-