Focusing on aerodynamics is important because they dominate the efficiency at high speeds but you can get pretty far without going to this extreme. For example

Focusing on aerodynamics is important because they dominate the efficiency at high speeds but you can get pretty far without going to this extreme. For example, the Honda CR-X HF was getting over 50 MPG in the early 1980's and it was a very nice looking car, mostly because it was small, well shaped and had a small efficient engine. The original 1.3 liter car (chassis code AE532) had an EPA Highway mileage rating of 52 miles per gallon (MPG)in 1984 and was reported to often achieve over 70 MPG in favorable driving conditions https://en.wikipedia.org/wiki/Honda_CR-X https://en.wikipedia.org/wiki/Honda_CR-X