For you aviation buffs, aircraft fuel economy competitions started after WW1. The two aircraft that won the British Lympne light aircraft trials of 1923, the ANEC1 and the English Electric Wren, both got 87.5 mpg (imp) = 105mpg (US). Pretty darn good considering the primitive engines of the day.
ANEC I - Wikipedia, the free encyclopedia
English Electric Wren - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Lympne_...ircraft_trials