I think that if you use Klotz, Gibbs or Brad Penn and i'm sure there is a couple more that have enough of the Zink and Phosferous There is no need for any addititve at all. But i suppose it wouldnt hurt to add it. I just talked to my engine builder and he said he would only warantee the motor if i used
oil with this already in it. Not using an additive. I don't know if he is trying to just have a warantee loophole which i don't thik so. But maybe he has found a difference i don't know.