I just had a really nasty thought. Hope Im wrong.
Suppose there is a glut of GI or GI+. In order to use it you would need 10-50% GII+ to make 10W-30. To make 5w30 you would need 10-50% GIII. But the kicker is you would need an increased additive package.
"How do we market this stuff?" "We just tell them the increased add package is to keep their engine extra clean..." "Yeah, we can call it "Deposit Shield" or some such nonsense..."