I missed one of your questions, Buckets. SJ is a later specification than the SG that Penrite produces. The second letter progresses in alphabetical order. It seems Penrite is not keeping up with the newest specifications from the American Petroleum Institute. I do not think this is anything you need to be concerned about at present: I think SG was probably current when the Vanguard engine was introduced in 1987, and I do not know of the engine having been redesigned since.
