Well Son of a gun.... Great Find! Its on page 211 of a manual I have:
"We recommend Castrol Edge Supercar
5W-50 motor oil for your Ford GT. If this
oil is not available, use motor oils of the
recommended viscosity grade that meet
the Ford specification of WSS-M2C931-C
such as Motorcraft® 5W-50.
Do not use oil labeled with API SN service
category unless the label also displays the
API certification mark."
I will still light my money on fire and use the Castrol, at least for the warranty period (and probably after that too), but stocking the standard Motorcraft 5-50 is easy for some other cars, and 05 GT is appealing.
Lastly the Ford GT team lurkers must find threads like this VERY amusing....
The hilarious thing about all this is that the owners manual states that if the super-expensive Edge GT isn’t available, then go ahead and use regular Motorcraft 5-50 ( page 207)