One thing to note about Royal Purple products is that they are VERY expensive. Engine oil, transmission fluid, and rear end gear oil are three fluids that take a beating by anyone that drives a Mustang like it's supposed to be driven, so spending outrageous dough on them is an economically wise investment.
I'd be willing to try their radiator additive, but I feel this job should be left to a product from a company that also makes a high performance coolant which is known to be FULLY compatible with the additive. Radiator gunk and corrosion deposits are complete poopswamp for an engine's ability to cool itself.
However, this power steering fluid, in my opinion, isn't nearly worth what I'm sure is charged for it. I'm not aware of the price, but I'm sure it follows the same trends their other products do. Bottom line: if power steering fluid is flushed and exchanged as often as Ford recommends it (every 30,000 miles), a cheaper raised-performance fluid, or even normal power steering fluid, will work fine. Hell, when we flush power steering systems at work we often use ATF V (Mercon Transmission Fluid 5), as this is allowed and recommended by FoMoCo.
There's my two pennies for your asses
