200 MPG Automobile
My comment is related to the drive line of the automobile. The transmission in the vehicle could be an infinately variable a hydrostatic drive that provides an infinately variable ration transmission that can be adjusted at random to any input rpm to output rpm within the capability of the unit that was selected for this vehicle. Overall efficiency of these units is approximately in the low to mid 90% when new. Other possible options for infinate variation is electric servo motors, or variable belt drive units.