I agree a small bit on the threads.Ive done thousands at work and do it on mine.I even use it on iron heads.I loved customers who thought you could go over 100K and years on a set of factory plugs.I had one that had over 230K on OE set.Came in as a no run.Pulled plugs and most of the plug was gone.That and antisieze makes them come out easy next time.Rocky