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]).
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).
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]).