Originally Posted By: Quattro Pete
Just because something is considered "synthetic" (group IV/V according to your definition), it doesn't automatically mean it's a great product.
Agreed. Royal Purple SL 5w-30 was believed to be primarily Group IV and some V. That doesn't mean it's a good fit for European cars with proprietary specs, nor would it be a suitable replacement for 15w-40 HDEO in a diesel application.
Originally Posted By: Fyrb4ll
Well, seeing as my truck is no longer under warranty, and the only spec my OM calls out is the anemic GM6094M, I believe the LM Vollsynthese[SM] will work.
Sure, but the engine won't notice the difference, except under longer OCIs, versus Quaker State conventional of the appropriate grade, which meets GM6094M.