100UL (Unleaded avgas) has finally been approved for spark-ignition aviation engines just in the past couple years.

Manufacturers have finally gotten approval to build/retrofit popular small aircraft with compression-ignition engines. These can burn Jet-A in a diesel cycle instead of 100LL. Jet-A is more energy dense than 100LL, and it is cheaper.

We’re finally in a regulatory position where the GA fleet can actually transition to unleaded fuels.