[mwebb]

the grille actually appears to be a duct , designed to direct a stream of high pressure air to flow right past the center of the wheel , thus masking any negative effects of the wheel itself

kinda like
an
"air curtain"

see the same thing on many newer cars , especially on
Volkswagen

Originally Posted by MetroMPG

Tesla will aeromod a version of its coming "Model S" battery electric sedan to improve range to 320 miles with the biggest-battery-pack option:

source: BREAKING: Tesla Making Faster 2012 Model S, 0-60 In Under 4.5 Seconds

I wouldn't bet a lot based on Musk's quote that the wheels are the only aero mod in play to increase range by 20 miles (6.7%). But it does imply that's the case.

But surely just about anything will beat the atmospheric blenders that have been shown on the demo cars: