Big engine or little engine, still takes the same hp to go a certain mph, all things equal on the vehicle.
but when the smaller engine makes 1/2 the power the larger engine does, it's going to be working harder at that same hp level.
No, they will be doing the same work, actually the bigger one would as it has to overcome friction from bigger parts or longer strokes or both.
+1 If a bigger engine got better or the same mpg tooling around we'd all have bigger engines in our late model cars... Throttle open more = better air and less work to overcome pulling air through the tiny straw of cracked throttle blades.
