Royal Purple is garbage. If you are going to pay THAT much for oil then you are doing it right with the Amsoil. I've never had an issue with Motorcraft blend oil though. All my cars use it and they all run great at $20 for a 5qt jug.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.