I'm trying to establish the year in which most oil companies began putting the standardized SAE viscosity grades (i.e., SAE 10W, 20-20W, 30, 40, 50, etc.) rather than "Light", "Medium", "Heavy", etc., on their PCMO packaging. I'm fairly certain that it was 1926 (at least, in the cases of INDIAN REFINING COMPANY and The Texas Company), but can't seem to locate any documentation. (The Society of Automotive Engineers said that the current grading system has been in place since 1911, but I KNOW that it wasn't commonly used on packaging anywhere near THAT early.)
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Jim Hinds
Columbus, Indiana
