To memory, cars started getting a lot more aerodynamic through the 90s. You have to go back to the 80s to find boxy designs throughout mainstream cars, at which point you’re looking at vehicles somewhere in the ballpark of 40 years old.

Anecdotally, I’ve not seen many of those on the road. It’s not too unusual to see a late 90s something puttering around town, but 80s and older is unusual, even in rural areas.

I drive a car that was released 25 years ago (a 7th-gen Celica) and it has a coefficient of drag of 0.32, which beats many vehicles currently in production, including multiple electric vehicles.

Now compare that to a car which would have been 25 years old, 30 years ago.

Someone driving the same car for a long time will have seen the change in numbers of insects getting stuck to it.