In the early 1990's I called all the majors, and asked how much oil (Group 4 & 5) synthetic base oil was in their "full synthetic" oils. The answer was the same across the board, at least 30 vol%. All had "Base oil" of conventional conventional base oil (Groups 1-3), at 70 vol% or less. So at one time, there was a standard were better market expectations and options.