If you look careful, the engine tach indicates ~1.2k rpm, the mpg readout at roughly 55mpg.
I've seen this stuff on Geo metros, or Mitsubishi Mirages, doing 35-50mph, but never on any vehicle doing 75mph.
It also kept that mpg rating for most of the ride. Just required extreme throttle precision, and a foot that won't move the throttle by even a single millimeter!
https://youtu.be/axH4_pB8fDE