Red Line Oil (great stuff) is not licensed by API. It is not SM nor SL nor any thing else.
http://eolcs.api.org/DisplayInfo.asp?Info=CompanyNames
Johnny, quit obsessing over the zinc content in the oil. Do some research on the ILSAC GF-4 Sequence III-G engine test. It is a tougher test than ever. And, as you've been told before, SM does not set max zinc limits...GF-4 sets the limits. In addition, any engine spec'ed for 5W-20 will run several hundred thousand miles on SM & GF-4 5W-20 without problems. More is not better.
http://eolcs.api.org/DisplayInfo.asp?Info=CompanyNames
Johnny, quit obsessing over the zinc content in the oil. Do some research on the ILSAC GF-4 Sequence III-G engine test. It is a tougher test than ever. And, as you've been told before, SM does not set max zinc limits...GF-4 sets the limits. In addition, any engine spec'ed for 5W-20 will run several hundred thousand miles on SM & GF-4 5W-20 without problems. More is not better.