Unfortunately, there are far more variables involved than were experienced with the transition for autos. UL was mandated for air quality reasons. The main reason for the rapid transition was that in 1975 catalytic converters became standard on all (?) cars, and lead would have killed them. Remember how performance went from somewhere decent to downright sucky? A Corvette with 190 hp? It wasn't until the mid 80's when microprocessors became prevalent enough to allow continual monitoring and adjustment of the fuel/air mixture that we started regaining some of the lost power.

Unfortunately, even with injected engines (those without FADEC), the mixture control is still manually operated. Engines of any power more than around 180 hp need more octane than is currently available except in small quantities. Removing the lead also leads to stuff like combustion chamber quench factors and more that I have no business discussing.

Bottom line: It's not coming up with an UL fuel that's the issue. It's finding one that is as happy in a 150 as it is in a turbo Bonanza at 18,000 feet. Without having to add engine controllers.