Larry, for a V8 I have read that 10 degree difference in the two cams at TDC is justification for chain replacement. Car will run and one may not realize the degradation in power and MPG. Of course, some chains jump without any prior warnings. It is best to know the history and keep up with intervals between changing of chains. No clean oil is going to make the difference of 50k vs. 200k, that is simply ludicrous and misleading. Most wear is dry start up and this occurs no matter what type or condition of oil is used.