RP, like Amsoil, only has one API certified oil. That is fine for your warranty. Anything not API certified exposes you to potential issues should something go wrong. Got that straight from a Chrysler Service Mgr who is very mod friendly.
I am being told over and over that this HPS formula does not benefit our engines because it uses hydraulic lifts. I've been trying to verify it without calling Dodge (for obvious reason) but I've found nothing to ease my mind......you see, I just put 7 quarts into my 2011 SRT8 6.4L and of less concern is that the tech I coresponded with by email with Royal Purple said the 10W-40 would be just fine if it isn't a winter driver.
After reading about the possibility of "clogging" and getting near certain my engine will NOT get extra protection with the HPS I am probably going to drain $75.00 in oil next week......I guess I can't blame Royal Purple but I do feel they advise outside thier otherwise stated recommendations too easy for a sale.
Amsoil is just a P.I.T.A. unless you pay for shipping but then it's extra costly over even Royal Purple. I love Royal Purple but I'd like to see them offer me a coupon but as I already said....I don't see them as obligated really.
Thinking about Redline now. They do use fully ester synthetics as base which is the highest quality. Amsoil doesn't even do that.
If you want a Royal Purple oil that is closest to the OE specification, then Royal Purple SAE 5W-40 (part # 01540, quart bottle) is going to be your choice. If you want the added protection and performance of a Royal Purple HPS oil, then Royal Purple HPS 10W-40 (part #31140, quart bottle) is what we recommend. Since you use your car primarily in the summer 10W-40 should not present any cold start issues for you. You can be confident that the HPS 10W-40 will be a fully functional significant performance upgrade oil. If warranty compliance is currently a more important consideration than a performance oil upgrade, then Royal Purple SAE 5W-40 would be the oil to choose. Thank you for choosing Royal Purple and have a great day!
Technical ServicesRoyal Purple, Inc."
So I went and installed it a few days ago......BTW, should I have a flush done to clean out this oil before filling with 5W-40 approved?