The way to compare apples with apples isn’t to compare two cars with the same powertrain, but to compare the major factors which determine the drag of a vehicle at any given speed, namely
– Mass
– Frontal area
– Coefficient of drag
The mass and frontal area are clearly higher for a bigger car (SUV), the coefficient or drag will be largely dependent on the vehicle.
Then you can also question if the powertrain in any given car could be smaller or more efficient to give further improvements.
We need to start treating our resources as scarce and be more efficient in our use of them