Appreciate your responses but I must not have identified what I was looking for. The API base oil groups have been well defined and much written about them. But, what I am looking for is how and when they came to be called Grp I, Grp II etc. I do not believe that the early oil industry called the early solvent refined oils Group I oils. But some where they began to be called that, Was 1509 the original name assigner? Was the first issue of 1509 the first time base oils had been divided into these five groups? I assume it was done for base oil read across purposes AKA saving money in testing. I am older than most of you but I cannot recall discussions on how the various groups got their spots. Thanks again.