Ponder this puzzlers:

 

At my airport, here in fly over country, 100LL self serve is $3.79/gal  and JetA (hand delivered to your personal fuel sucking jet) is $4.15/gal.

 

Europe is trying to phase out 100LL and it seems that the price of 100LL is far greater than JetA across the pond.  Diesel engines make all the sense in the world for those overseas aircraft.  Not yet, not here, not now.