From what I've read, having high
zinc is only half the solution. Modern oils have higher detergent levels. These detergents "clean" the
zinc off metal surfaces. Accordingly, a
zinc additive is ineffective. Oils like Joe Gibbs have lower detergent levels as well as higher zinc content.
So, if your engine will benefit from higher zinc levels, it is probably wise to use an
oil formulated with it instead of trying to add it yourself.
Regards,
Kevin