Two airmen were court-martialled at Binbrook in 1951 for stealing petrol. As I recall from childhood there, my father told me it was impossible to fully drain the tanks of a Lincoln in normal tail-down stance, so the remaining dregs were allowed to flow onto the dispersal and the surrounding grass. The airmen had collected this Avgas in a mop bucket for use in their motorbikes, and paid the price in jankers ...
Prolonged use of avgas 130/145 will knacker valves and seats of roadgoing engines. Less exotically, my Austin Champ (£47.10s in Army disposal auction 1967) ran beautifully on a 50/50 mix of three star and paraffin, just as well as it did 13 mpg whether driven hard or gently, with trailer or without.