Originally Posted By: j454
Thanks guys, I'm just trying to figure out if M1 is different now compared to the way it was prior to the lawsuit with Castrol when they "Castrol" first got away with calling group III oil "Full Synthetic"
I assume that this is why this group III "synthetic" oil is compatible with dino oil??
This leads to another question; are group V oils compatible with dino oils too. Or how about group V & group IV and so on etc.?
And back in the day it was a concern not to mix synthetic oil and dino oil? What has changed? Thanks
Yes, M1 is different now than before the "Castrol" thing, and it does now contain some Group III base stock.
Part of reason for that was no doubt to reduce costs and remain competitive, but probably Mobil became more aware that Group III base stock could be added to PAO/Ester stock to make a very high quality oil.
AFAIK, and according to most oil companies that I know of, there is no "general" problem in mixing conventional, Group III, or Group IV/V oils together, and most additive packages end up doing just that to some degree. At one time there was a concern about switching from conventional oil to PAO based oils because it caused leaks (seal shrinkage), but that problem has been corrected in modern oils.