This is such a mess, and it highlights how ineffective the FAA has gotten. I don't want to hear them act like this is an "abundance of caution" when this very same organization pushed the 737 MAX right through. Maybe the problem is that George hasn't greased enough palms?
Pilots WANT unleaded. It's better for the engines, but more importantly, it nullifies concerns from the general public about lead emissions causing health concerns. Which isn't to say those concerns are even scientifically valid, but given the option most pilots would gladly pay a bit more to be good neighbors.
I disagree that unleaded is better for engines. These engines were designed for leaded gas; the lead serves a necessary lubricating function. That doesn't mean there will not be an alternative, or even a possible modification to the engines.
What little lead fouling I have seen has been on plugs from running too rich a mix, and that can usually be "burned off" easily, or cleaned manually.
Lead used to serve a necessary lubricating function way back in the 1930s-1940s before the invention of Stellite valve seats, and other hardened alloys for valves. Any aircraft engine that has been either built or overhauled in your or my lifespan already has hardened valve seats installed, or it is a fairly minor procedure to replace them as a part of a top-end overhaul, which often does not even require the engine to be removed.
A far worse problem than lead fouling, which just electrically shorts a spark plug and results in power loss and annoying vibration, is lead deposit preignition, where hot bits of lead oxide deposits adhered to the piston act as preignition site triggers, resulting in detonation. Despite the violent sounding name, it will typically go unnoticed by the pilot unless they have automated cylinder head temperature monitoring and alerting, which the majority of piston powered aircraft do not have. At cruise power it can destroy an engine within a minute or so.
The notion that lead was good for engines was always just propaganda. One of the main reasons engines last so much longer today than they once did is the lack of lead in the fuel. (Lubricants are better, too, but are also no longer damaged by lead contamination.)
General Motors, in originally promoting leaded gasoline, was aware of this at the time. They did not see reduced engine lifetime as a problem to be solved.
Pilots WANT unleaded. It's better for the engines, but more importantly, it nullifies concerns from the general public about lead emissions causing health concerns. Which isn't to say those concerns are even scientifically valid, but given the option most pilots would gladly pay a bit more to be good neighbors.
It's just beyond frustrating to watch.