Quote:
Originally Posted by 2000mc
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* An American Motors Javelin had a cosmetic roof spoiler which made no difference to performance.
* One Toyota Celica Supra also had an iconic, cosmetic roof spoiler, also of no effect.
* Mercedes-Benz built a 190 Evo, with a combination roof spoiler, rear wing, which was effective aerodynamically.
* Today's SUV rear spoilers have been shown to affect drag.The further back they reach, along the Kamm-Back contour, the lower the drag and lift. You can see it between the Porsche Cayenne and Toyota RAV4. The Porsche is Cd 0.36, while the RAV4 is Cd 0.30, and Toyota went to great pains to extend the D-pillar extensions back, almost to the Kamm truncation line.
* As MetroMPG emphasized years ago, we ought to take vehicles on a case-specific basis, and steer away from generalities.