I've been reading about NASA's experimental GL-10 Greased Lightning tilt-wing aircraft with interest.
My understanding is that this is a diesel-electric hybrid aircraft uses stored electrical energy to satisfy the much greater need for thrust during takeoff (and landing?), but for regular flying runs off fewer propellers powered by the 2x 8hp diesel engines (which presumably also are recharging the Li-Ion batteries for the next takeoff/landing) to achieve better efficiency.
The answers to this question show that diesel engines are generally poorly suited to aero applications, generally due to weight and complexity.
Why then does the GL-10 use diesel fuel instead of more common aero fuels?