Cost factors in of course. TGMO up here is cheaper than just about any off the shelf oil, even when that off the shelf oil is on special. On the other hand, Motorcraft oil isn't readily available here outside of dealers. Nissan/Infiniti has an agreement with Mobil, so you're getting Mobil products you can buy anywhere else. AC Delco oils are available outside of dealers here, all the while a few GM dealers (and others) are pushing Castrol.
Generally speaking, I wouldn't think that the majority of OEM oils are any better or worse than what's readily available on the shelf. Sometimes, it's the same thing as what's available on the shelf, and others, it's something more proprietary, and others again, it's just whatever a dealer/OEM gets cheapest.
Generally speaking, I wouldn't think that the majority of OEM oils are any better or worse than what's readily available on the shelf. Sometimes, it's the same thing as what's available on the shelf, and others, it's something more proprietary, and others again, it's just whatever a dealer/OEM gets cheapest.