Good question about the size.
I've been using 13/16" SAE and it works fine, but I figured the lug nuts were actually metric like everything else. 13/16" is about 20.6375 mm.
If they are the same as my '03 (and I assume they are) they're 21mm. The torque spec on mine is 82 but I usually set the wrench at 80. Haven't lost a wheel yet:dancin: