[lunarhighway]

i think what frank is saying is that aerodynamic drag is not the only factor influencing fuel consumption, there's rolling resistance, vehicle weight, the gear ratios. also aerodynamic drag increases with speed, so vehicles driven at slower speeds will see less benefit from aero improvements that vehicles driving a lot at highway speeds.

thus mathematically a 3% reductions in aero drag equals not a 3% improvement in FE.