I think you first have to to understand what numbers like 0W-40 are. Than you'll have to understand that these numbers are only a very rough indicator. Cinematic viscosity, pourpoint and other indicators will determine an oil much more. There are also things like detergents, friction reducer…
Next problem is that oil manufacturers never will tell you how their oils are formulated in detail. And each oil manufacturers will say his one is the best. So if you read things on the internet please allways check who has written the artilce and what might have been his intention.
ZDDP (zinc-dialkyl-dithio-phosphat) is also available as an oil additiv for regular motor oils. Also there a a lot of oil manufacturers that offer oil with ZDDP for classic cars.
They put ZDDP out of the oil, because zinc will destroy catalysators within a short time. So if you don't have emission laws in your county/country, there is nothing against the old school ZDDP oils. If not, maybe you should think twice.
And yeah - another oil thread.
