I recently secured a 2016 R8 V10 Plus from a McLaren dealer, for a customer of ours.
Once we had paid for it and arranged delivery, it went straight on the dyno for a tune and wasn't responded as hoped.... It turns out they brimmed it with 95 RON and after a call to the McLaren dealer, admitted to it!
The dealers are not the factory!
But goes to show you the difference the fuel makes.