Huperlube
 

I use ZDDPlus.

4 oz bottle restores 5 quarts oil to SF level of Zinc and Phosphate

Ingredient is Zinc Dialkyl Dithiophosphate. CAS 68649-42-3

Made by Zplus LLC in USA

Intended for offroad use and racing vehicles only.

Less than $10.

Heres one some from "Eastwood, it has to be good from them.
ZDDP Engine Oil Additive Zinc & Phosphorus 4 oz
http://www.ebay.com/itm/360432397120...84.m1423.l2649
Its only around $14.