If the oil carries both CK-4 AND SN licenses, then the chemical limit of SN applies. That means lower zinc levels, the same as any modern passenger car oil. Rotella T4, T5, and T6 all carry the CK-4 designation now (since sometime in 2016), so their zinc levels have been reduced. Rotella T1 does not meet the CK-4 designation. Not sure about it's zinc content.
