Purchased a '93 R100RS a couple of days ago, with it, seller give me six quarts of PennGrade 1 Partial Synthetic motor oil. I had never heard of it however, the labeling states, "Meets no current API classification", that seemed a tad concerning. Then I Googled it and apparently it is well known to the racing world. States it contains high levels of Zinc and Phosphorus. It does state to be wise to the fact it could be detrimental to cars and trucks with converters. Of course this '93 does not have a converter. I'm thinking perhaps that's reason for not having a API classification. Anyone have experience/knowledge with this oil?