SN does not necessarily mean low zinc. The reason is that straight wt oil, any multi 40wt, or higher, and some others aren't dictated by SN. For instance, M! TDT is SN with 1100 ppm of zince, their 0w40 is SN with 1100 ppm zinc, etc. SN only regulates certain viscosity oils, which I'm thinking is 40wt and up, neither do I think it dictates zinc levels in HDEO oils even though they are dual rated. Funny stuff. I wouldn't get all worked up over zinc levels until they go below 800ppm or so, for any oem engines of recent manufacture. There are other anti wear additives and the technology marches on, while we worry too much.