This is my point - 10W30 doesn’t need to meet the approvals that 5W30 does (i.e. D1 Gen 3) , so when another round or two of more stringent approval updates comes into play where does that leave 10W30 ? I’m merely suggesting that the reasons I would use 10W30 in a GDI engine (less sheering , lower NOACK , less VII’s making for less deposits) may eventually all be able to be accomplished with newer approval 5W30 . oils . Where does that leave 10W30 ? How much future R&D is going to go into R&D for an oil (like 10W30) by major oil companies which does not have to meet more stringent upcoming approvals outside of GF-7 and what ever follows SP base approvals) ? Perhaps it’s already happened : M1 10W30 EP vs M1 5W30 ESP possibly makes 10W30 obsolete ."All other things equal" I think it would be more durable. But the problem is things are never equal. And the fact that 10w30 doesn't need to meet any approvals means it just costs less to produce to get the same result as a 5w30.