Motor oil for older engines

["Jay" <jciampi@xxxxxxxx>]

I was reading a "tech Tip" in a Nash Club regional newsletter the other day 
stating that we, who own cars with pre-cat.converter engines, should use 
Diesel motor oil as it still contains ZINC for lubricating cam lobes, 
valves,etc.
Modern engine with Cats don't need  Zinc as they use hardened parts and Zinc 
will totally ruin a Cat.  Modern gasoline engine motor oils do NOT contain 
any Zinc for that reason.

Anyone out there that confirms that we need Zinc or  can refute the 
statement that Zinc isn't  necessary?  I have never looked at a bottle/can 
of diesel motor oil to what it contains, so I have no idea if this is a 
genuine concern for older engines or not.  if your engine has been 
overhauled with modern components, Zinc would not be necessary for your 
engine lubrication.

Jay in FL.