As far as Royal Purple synthetic oil, save your money and use the Motorcraft blend. Ford uses it in most of their products and does more testing than all the independent oil companies combined. You know why the big name racers use and promote the specialty oils, because those oil companies give it to them. If you really want to spend more on specialty oils, use Mobil1 or Amsoil, both were around long before Royal Purples' engineers were even born. Full synthetic oil is great for constant high temp, high rpm engines, but a 6.2 isn't either one. Synthetic oil, whether it is a blend or not, is still crude oil, just refined differently, there is nothing actually "synthetic" about it.