My machinist warned me about that. He said you can have to much zinc. He said for running the Lucas classic oil would be fine but he recommended that i not use it and the zinc additives together.
I would agree with that. Lucas has been making oil products for a very long time. If something they made was "not right" we'd all know about it by now. It's good oil. I've run it in Gladys now for right at six years with zero issues. I don't run it in Vixen, because she sat up since 1980. I warmed up "that oil" and then changed it to 10/30 synthetic with one quart of Marvel's Mystery oil. Ran it like that for about 1500 miles, changed it to the same thing again for a full oil change. Changed it after a full oil change, added some STP and that's "still" where I'm at. You should have seen the blackness that came out on each change. I think I saved that little engine. Probably why it continues to run so well.