You do know that Plat and Ultra are Grp III oils?
SOPUS has been forthcoming in stating that they are.
With M1, it will depend upon the grade, so other than drawing inferences based upon PDSs and VOAs/UOAs, nobody here really knows.
XOM isn't telling.
To me, there is a dividing line between oils suited to long drain intervals, and those that aren't, regardless of the blenders' claims.
Pennzoil does not promote either PP or PU as extended drain oils, but both seem to hold up well on long runs, judging by how the oil looked in various UOAs.
If you check out the UOA section, there are some good UOAs with PP, PU, old Edge and M1 in various flavors out to 10K+.
OTOH, Synpower does not seem suited to long drains, although it holds up just fine on shorter ones.
Syntec does come in at least one long drain flavor, and vanilla Syntec seems to hold up better than Synpower, although there aren't that many Syntec UOAs
The jury is still out on G-Oil.
There is one very good 10K UOA of this oil in that forum, as well as two mediocre ones on shorter runs.
