Thanks for the kind words Mark. I try to do my best and share my mechanical background with our ownership brotherhood. There are however, many other equally talented and very knowledgeable owners who share this special Forum.
After attending Dave's Rally 1 in Detroit and having extraordinary contact time with engineers who were lucky enough to be selected to participate in the FGT program, I became convinced the design team recommendations were very well thought out, researched and the team had tested and collected supporting data for these recommendations. The certification/qualification testing our car went through during development speaks volumes to the final trouble-free supercar product we owners still enjoy now years after production ceased.
When our special 5.4L engine was developed, a new full synthetic Motorcraft 5W-50 oil was simultaneously introduced specifically for the GT application. I realize many owners are passionate about "their" oils and numerous threads discuss the use of using other brands. That's fine, use what you like. Knowing the development testing which went into the Motorcraft fluid GT recommendations is a no-brainer for me and is what I use exclusively. This applies to engine oil and very importantly the transaxle as well. If you have a difficult time finding the specified products, Torrie on our Forum can ship them to you quickly and give you a fair price.
And Mark is correct, when the Motorcraft 5W-50 first came out it was exclusive to the FGT application. Although I do not think the oil properties have been changed, just an increasing scope of applicability. Since 2006, this same oil recommendation has been extended to other Ford high-performance products, GT500 and Boss 302 applications.