[2] Autoevolution "The Calibra holds the title of having been the most aerodynamic car in the world at its 1990 launch, with a drag coefficient of just 0.26."
[1] TopSpeed.com "It was, however, the most aerodynamically efficient Opel ever with a drag coefficient (Cd) of 0.26. It remained the most aerodynamic mass production car for the next 10 years, until the Honda Insight was launched in 1999 with a Cd of 0.25"