I guess the boxy 'old' 2001 Lexus LS-430 reigns supreme once again at a
.25 Cd.
The standard LS-430 had a .26 Cd ( same as the Prius ) but could be purchased with the optional air suspension system that lowered it to a Cd that outdoes the Prius.
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I see a lot of 'design room' between the shapes of the Prius and the LS-430.
I almost laughed out loud when I read Honda's excuse for copying the shape of the Prius ( They stated that they had to shape the Insight like the Prius to get the same aerodynamics out of the car )