100mpg equivalent and he didn't even touch the aerodynamics of the car? Hell, it's even a Mustang coupe with that nice refrigerator-shaped roof line.
He would be lucky if it only took 20hp to maintain 55mph with that car. The BSFC of the engine would have to be around 0.18lb/hp/hr to hit 99mpg, assuming a gallon of straight gasoline weighs 6.5lb.
This is also ignoring the fact that he's using a stock block with a valley girdle. Oh, but the 500ft-lb engine will last forever that way.
View attachment 312127
That and absolutely no details on how he's getting 100mpg.