Guess I am the winner till this point... 140 mpg!
Unfortunately I don't have a picture of my own scooter Bajaj Legend, but it is the model in the pic below, a 4-stroke 150 cc, which gave ~ 11 bhp, and was a breeze to ride till ~50 mph. Beyond that, it was an invitation to ER - these vehicles are notorious about ride stability. It looked something like this...
It routinely gave me 60 kmpl (~140 mpg US) from 1999 to 2004 when I sent it to my brother who needed it. Now my brother has graduated to a car, and the scooter rusts in the front yard.
In India, some 100cc bikes like the one above (by far the most popular ones) better even that, going close to 200 mpg - that too sipping a cocktail containing more naptha than gas!