I went out today and bought a whole bunch of Mobil 1 15W-50. All of it is rated SL/CF which has a good amount of
zinc - 1376 ppm per the Bob
Oil Guy website. That is a great site by the way. There appears to be a lot of the old stuff on the shelf still, at least in Las Vegas. In fact, I could not even find the newer SM rated oils except for a 0W-40. At least I now have time to investigate different products.