Well, another year has come and gone, and with it a number of questions and comments from you readers. They are always interesting to me and certainly have made me aware that there are terminologies, organizations and tests in the engine oil industry that defy understanding without some sort of cheat sheet. The questions that came up this past year were primarily related to API 1509, the Engine Oil Licensing and Certification System. So I thought I would tackle the questions in a systematic way to identify some issues and possibly add some level of clarity to the subject.
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