My only experience with RP was with the RP XPR 10/40 or known as Racing 41. I used it because I was running WMI (Water/Meth/inj) at the time and needed an oil formulated for use with alcohol fuels. I ran the oil for about 10K miles.
I never had any problems with the oil other than it seemed my car used a little oil, about 1/4 qt in 3K miles. Well within normal, especially on a car with 380whp. BUT, the WMI kit came out, and so did the Racing 41.
I have now been back on M1 EP for about 6K miles. Using 10/30 EP and it uses NO oil in 3K miles. So I am confused. 40w I lose oil? 30w I don't. I will just chalk it up to the 60whp difference in my car now, vs then. I also noticed ALLOT of lifter tick with RP and None with M1.
Now the Reason why I am considering RP XPR 5/30 is I don't think the RP itself caused the lifter tick, but the thicker viscosity did. Even though, it is a 10/40 vs a 10/30 I wouldn't think it would make that much of a difference at start up but it did. Even when the engine was warm the lifters ticked. M1 no tick.
Not to rule out RP, I think they make a good oil, but the claims are just WAY OUT THERE. Then again, Amsoil does the same thing, Claims, Claims and More Claims. Only "Claims" I believe are ones I see with my own eyes, and on my own account.
Then there is Redline, that is one company that just stays quiet, never makes "claims" and just sells a good oil in the quiet. For some reason I want to give their oil a try too. Only thing I am worried about with Redline is if the Esters will prematurely wear out my Turbo Journal Bearings. The end caps of these bearings are Brass, and being a soft metal, I am kinda worried how Esters will affect it over time.