My uncle was on the small team of aircraft mechanics at Shannon Airport (Ireland) in the mid 50’s. (A guess at that date) Affiliated with TWA, but whatever landed and needed fixing, you fixed. He would have been about 24 at this time.
They ran av-fuel all the time, “it was great, we could advance the timing real far, and the Old Jag engine roared!”
only the airport customs guy knew they had access to un-road-taxed fuel, so he regularly dipped their tanks. So they all made brass “top hats” that went into the filler neck and held 2 cups of road fuel.
and it burned real black, so customs guy used to finger swipe the tailpipes, so they all had fishtail exhausts you couldn’t get your finger into, like the Harley guys.
He said his wife told him, “you know the dog wakes up and goes to the door when you are still 3-4 miles away, that car sound is unique..”. Yeah it is!