I won't like to speculate when it would be safe to do such treatments Doc. I have seen the damage it does whilst working at Suzuki when three old timers from a local rummy club got three Suzuki alto with a serious oil eating habit. These three chaps were old school from the redex days on the heights of the leaded fuel days. They thought by putting a famous US oil treatment and running it for 3000 miles on brand new engines would a good idea. After fully knowing the damage it can do I don't recommend it on engine with perfect health.