I went back through my correspondences with castrol and found they suggested Castrol Edge 25w50 for flat tappet engines as it has one of the most zinc in castrol range - 1150ppm.

Note it is API SG (which is probably due to other things as opposed to lower quality). WHat I mean is, its probably API SN grade with regard to _____, but due to the high zinc and other good stuff you can't do with SN, it only "meets" SG in this regard
Nulon still has 1300ppm

Last edited by Tyler; 14/10/20 12:03 AM.