I'm pretty sure Ferrari tells owners to use only Shell 10w60 in their Enzos as well....but it's not the best oil unless you race your car.
http://www.bobistheoilguy.com/forums...017431&fpart=1
It's not mind boggling at all, a motor works more efficiently when it has to work less to push the oil around...provided the oil does not allow metal to metal contact.