I sent Amsoil if they have lowered the amount of zinc and P in this oil to meet API and Jim V said as of 6/3/03 they have not and the latest scan said P was 1112 and Z was 1235. So who knows. NOAK is down to an impressive 5%. Patman, this is a great oil for a C5 I would think! Very good price/performance ratio....can I say that?