I do believe this oil damage issue is more during the breaking-in of rebuilt engines. If your talking about older engine which have miles on them, I don't think the lack of ZDDP is as big an issue. There have been reported very early engine failures (usually cams going bad) when not using a ZDDP additive while breaking in newly rebuilt engine. I just rebuilt an engine on my Triumph TR3 and I purchased a ZDDP oil additive for the break-in period. I haven't started it yet, but I did do a fair amount of research on the subject and this was what I concluded about the oil issue. Considering I have several older cars, for PEACE OF MIND I do add a ZDDP additive to all my older cars oil once every several oil changes. But that is just for precautions.