Originally Posted By: HouseTiger
Originally Posted By: bluesubie
Some good comments from Doug Hillary in this thread:
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2716911
He ( Doug Hillary in that thread posted ) made a statement that any diesel oil that is not also rated for gasoline engines should never be used in gasoline engines. So, in my 92 Explorer, it has run Shell T6 5W-40 since the product was introduced. Runs fine and cleans things out. I've also run the T6 5W-40 in all my Honda bikes.
According to Mr. Hillary, now that Shell T6 5W-40 has dropped the "S" rating, it shouldn't be used in gasoline engines; however, that same 5W-40 that is not SN rated does carry the JASO MA2 rating, which IIRC, is a gasoline engine rating.
Can't see any reason to stop using Rotella 5W-40 in either the truck or the bikes merely because one rating was dropped. If I'm wrong, someone please advise.
Not to speak for Doug, but perhaps one reason that he only specifically recommended dual rated HDEO's in petrol engines is because if an oil was not dual rated perhaps the phosphorus levels would be far above what we have now in your RT6 example. While we can guess that perhaps the reason that the new RT6 5W40 isn't dual rated is possibly because Shell felt like it wasn't worth the cost since petrol engines is not the intended target. Maybe Shell just didn't want to take a chance due to the existing phosphorus levels (see Chris G's comment above).
Also note the reasons that people first starting using HDEO's in petrol engines was because of poor petrol engine standards at the time. And of course, "Modern appropriately classified lubricants as recommended by the engine's Manufacturer have almost effectively negated their use in petrol engines today IMO".
Personally with Mobil 1, Pennzoil, and Castrol 0W40 being readily available at Wal-Mart, I don't think there is really a reason to run RT6 in a turbocharged Subaru any longer. If I want something a little more robust than a light 0W40 based on uoa results or oil pressure , I'd probably run a 5W40 or 10W40. Or if I wanted a robust 5W30, I'd run Castrol Edge 0W30 or Red Line/Motul 300V 5W30.