It has more to do with the improvements in engine machining, and metalugerical advances than anything else. It used to be common to run 20 to 25% in ignition 2 strokes. Back when I was first starting to run model engines, we ran White gas (coleman fuel) mixed with 70 wt. oil. The lifespan of some of those engines were measured in minutes. Some of the slag engines would wear out in a short time.

Bill, AMA 4720
WACO Brotherhood #1