AMSOIL just posted a tech bulletin which I have attached below. It just discusses the possible problems with additives if the contents are unknown or mislabeled. There are many additives on the market. Of the 4 they looked at, I'm only familiar with one.
In any case, if using them, just be sure you know what's in them.

additive bulletin

 

wow - good info there

There was a long discussion here about Prolong i believe

 

thanks heath good info but what really suck is when there is supposedly no chlorine in a product and there is i dont use additives but somebody who does thinks that there additive is good and still have bad crap in it