[marcus0x62]

There are already alternative engines in wide use (particularly on ultralights and light-sport aircraft) that can run on regular, unleaded gasoline, like the Rotax 912[0]. The issue, as others have pointed out, is getting these newer engines certified for use on existing, older planes. This would require extensive testing to get a Supplemental Type Certificate (“STC”) to allow the engine to be installed on a certified aircraft (think anything manufactured, like a Cessna 172 or Piper Cub.)

0 - https://en.wikipedia.org/wiki/Rotax_912

[bdefore]

I wonder if this extensive testing could be funded by a tax on leaded fuel. Seems like this would benefit everyone.

[marcus0x62]

Sure, or the FAA could just go ahead and approve G100UL[0] and save everyone the trouble of an engine swap.

0 - https://www.avweb.com/insider/faa-continues-to-stall-on-g100...

[HeyLaughingBoy]

Except the people who have to pay for an engine swap.