Stand back. Oil questions on this forum = burning match + puddle of gasoline. Lots of strong opinions.
But here goes. I'm not famiilar enough with Royal Purple to comment on it, however I can tell you this: I switched my HT-4100 '87 DeVille to Amsoil synthetic 10W-30 ASM two years ago, and send oil samples to Blackstone Laboratories for analysis at each change.
I change my oil twice a year, usually 3500 to 4 thousand mile intervals. The wear metals content is now 62% lower than the universal averages for engines of this type. I did get a small bump in aluminum and iron on the last test, but it may be because I took the sample from the filter instead of the drain stream. The TBN of the Amsoil was very high, almost new, even after 7 months in the crankcase. The oil lab has recommended I extend my drain interval to 4500 miles.
This isn't a pitch for Amsoil. I don't sell it, or cheerlead for them (at least not here). Just my experience. My point is, if you want to experiment with a product, don't be afraid - just follow Ronald Reagan's advice: Trust but verify.