If you have a draggy car it's not going to do any wonders for your fuel efficiency either. The production GT-R is actually supposed to have a really low Cd and the frontal area is pretty equalized though, but still that big inset grille on top of the bumper doesn't look like it's doing any favours for downforce or drag in silhouette car form. Also take some note about how the low width and rounder corners of the road Supra gives them a much bigger free area for the front fender flares.
