Let's say that we have a mid-1950s "gas guzzler". Now, we take away the exterior "shell"/chassis and replace it with a modern car's. That is, it will visually look just like a modern car from the outside, but it's still using the exact same engine and technology inside.
Now, would this "improved" 1950s car drink less gasoline just because it has a different, "streamlined" shape? Or is this just a myth? Or is it technically true, but so insignificant that they might as well have kept on making beautiful/unique car models instead of making them all look the same?
I'm no physics/airflow expert, but it's always struck me as strange to hear how much the shape allegedly matters. Something tells me that what really matters is 70 years of continuously improved gasoline engines, further motivated by the increasing petrol prices.
Am I way off or close to the truth? I just have a very hard time "buying" that the shape could matter so much. It seems to me that if somebody in the car has had a hamburger recently, that extra weight in their body will more than make up for any "car shape-based gas-saving benefits".