The thing with royal purple is i dont see any benefits at all and i can only see the disadvantages =(. I was told by a lot of other car enthusiast in my area to use RP and they swear it's the best out there. With doing very little research i went ahead and bought a dozen cases of them (almost at wholesale prices) for the 6 cars I have at home. I was doubtful though and never got around to putting it in my nsx.
The result with my other vehicles? I was disappointed and didn't see any differences. (THAT DOES NOT mean it is not better than the other leading oils, it is just that I didn't experience anything different). Also, i love the color purple, but putting in purple stuff in your engine makes it absolutely horrible to check whether your oil is dirty or not, it almost immediately turns dark brown (which they claim due to the detergent cleaning out the engine that was left from previous mediocre oils). But on my 02 odyssey van, (that I change evey 3.5k-5k, and I used RP for 5 changes, its still the same....hmmm, i must have a VERY dirty engine.
Also, the RP seems to lose its "lubricating" effect rather quickly. When you pour that thing in the car does run more quiet, but not for long.
I have been using mobil 1, amsoil, and eneos and all those did a splendid job. Same drain interval, the amsoil and eneos still comes out with a golden glow. on my 350z (and i have no idea why... doesnt happen quite drastically to my other vehicles) when i changed with enoes, it completely transformed the vehicle, i revs faster, drove smoother, and tracked harder. i couldnt believe it myself but it even shifts better!!!
With oil, its pretty much a personal thing, so in all honesty just go with whichever brand you prefer!! But with my experience with RP, I dont think i'll be paying up for it any time soon again. Heard they have a new formula (MORE expensive stuff) call HPS, maybe thats better?
sorry for turning this into another oil discussion, i dont intend it to be. just my thoughts about RP, never did any UOA or tests besides just driving it. Thats all.