Originally Posted By: Reddy45
I'm not a pro at this stuff, but to give you a somewhat useful answer...
Moly provides cushion/lubrication between SLIDING surfaces (like cam journals). It breaks apart at very microscopic levels and retains its form, and glides between opposing surfaces.
Zinc.. I think works best when in combo with Phosphorous? ZDDP which is a well known anti-wear additive. I forgot the actual mechanism but it constantly forms a sacrificial layer between surfaces that takes the brunt of the friction.. something like that.
That's how I understand it also. I use Rislone ZDDP additive a lot, it also contains Phosphorous, half a bottle in a 5qt sump brings the SN oils up to 1200 ppm and the bearing wear levels dropped significantly in one particular high output engine, so it does a lot more than than just protect the cam and the numbers prove it.
Like anything else though people get carried away, if 6 oz works well then the who bottle will work better (it doesn't) and that's where the problems start. It is not needed in new engines that use different bearing materials and OHC with light loads but engines that spec SF, SG and so on really seem to benefit from a little extra zinc.