[S201]

It's not that there's not a demand for unleaded avgas, I'd say most GA pilots are ambivalent to leaded vs. unleaded fuel; they just want whatever makes the prop spin.

The issues with the unleaded avgas rollout are purely bureaucratic. The FAA has been dragging its feet for literally decades to get it done. Even when we have fuels like G100UL approved which is a drop-in replacement for ~80% of the GA fleet, it still takes forever to get across the finish line.

[histriosum]

Indeed. G100UL is drop in for the entire piston GA fleet, though, not 80percent.

[sokoloff]

> the entire piston GA fleet

All the spark-ignited piston fleet, but not the diesel piston fleet (which cannot use G100UL [nor is it needed for them as diesel is already unleaded]).

[cjrp]

Aren’t they using Jet-A anyway?

[sokoloff]

In practice: yes; kerosene (Jet-A) and auto diesel are very close compositions, with the former flowing better at low temperatures (as might be found high in the atmosphere). Jet-A comes out of convenient pumps already located on airports.

They’re part of the piston GA fleet for which that fuel is not approved (and neither safe nor needed).