I find automatics in 'D' will try to keep themselves in too high of a gear (practically idling around, presumably to save fuel) so a downshift is needed to acce

I find automatics in 'D' will try to keep themselves in too high of a gear (practically idling around, presumably to save fuel) so a downshift is needed to accelerate 'S' behaves more like a human driving a manual - I assume the MPG and emissions testing is done in 'D'