Horsepower is not the answer. The Audi Q4 Sportback e-tron's sloping roof can improve efficiency without changing motor output, because a car's energy bill depends partly on how stubbornly it pushes through air. Shape does the work. Audi quotes a drag coefficient as low as 0.26 for the Sportback, against 0.28 for the upright Q4 e-tron.The rear deserves the attention. Where a blunt body can leave a...More