1987 GM Aero 2003A concept
 

If the link works, this is a follow-on project based upon the 1982 GM Aero 2000 ( Epcot ), 1983 GM Aero 2002, and 1984 Chevrolet Citation-IV concept cars, Cd 0.23, Cd 0.14, and Cd 0.18, respectively.
A guess for the 1987 variant would be in Cd 0.13 territory. So far, it hasn't been reported, and no confidence that it ever will be.
As with all concepts, one must take into account whether they were 'running' prototypes, or, simply 'gliders', with no engine, powertrain, cooling system, etc..
Also, electrification of these cars could allow actual Cds to approach those of the non-operational concepts, as cooling systems would only be sized for around 30.8% of an ICE.
Synthetic vision could allow a virtual 'mirror-delete.'
'Cooling plates' could supplant what's left of the radiator, leaving only a small porosity requirement for air conditioning condensers.
https://www.google.com/search?q=1987...gKDKiUgbfAh_OM

It verks!

https://static.wikia.nocookie.net/cl..._Cocept_01.jpg

Makes me wonder how an aviation-inspired air-cycling setup, instead of the more usual vapor-cycling air conditioner, could lead to further improvements to the aerodynamics. Or if that wouldn't be doable at all... AFAIK the only road-going vehicles featuring some sort of air-cycling conditioner are some coaches, due to Covid-related regulations which prompted coachbuilders to resort to this in order to decrease the risk of contamination, yet I'm not sure how effective it is.

If you're too hot you ain't high enough yet. I carried light coats for when I had to fly at 10,000 msl even in 100 degree summer Socal days.

My father is more familiar with flying on non-pressurized aircraft, as he went from my hometown to Guaratinguetá in a C-130 when he was 17. Once I had a chance to go on a test-flight in a Maule aircraft from the '40s, which I refused because I didn't like how the runway was in much disrepair to say the least, while my father was too excited to refuse the invitation... I guess I have already bragged about my aeronautical familiar background a handful of times BTW :D

I don't understand why old cars with outdated design keep being discussed.

"Don't criticize what you can't understand, your sons and your daughters are beyond your command...." -- Bob Dylan

This is a new car:

https://blogger.googleusercontent.co...71453599_n.jpg
https://blogger.googleusercontent.co...21474376_n.jpg
justacarguy.blogspot.com: Historic and Vintage Restorations in Australia continue to use traditional coachbuilding methods to make this 1939 Alfa Romeo 6c 2300 MM, which started off as only an original chassis and driveline sourced from Europe, designed by Michael Simcoe (once head of GM design global) in the Touring style to resemble the 8C 2900 Espada of Ralph Lauren

The 1987 car aerohead posted has a Cd likely lower than anything being sold today.

'understand'
 

Perhaps for the same reason AeroVironment / General Motors discussed Paul Jaray's streamlined half-body of 1922, when designing their GM Sunraycer of 1987.
Aerodynamics is agnostic when it comes to calendars. Just ask a peregrine falcon, gentoo penguin, bluefin tuna, or porbeagle shark.;)

What I do not understand?

It is a retro car.