Keith is correct, I use rotella exclusively and read sometime back about the elimination of
zinc. Dow makes a lubricant, 'M-Gear
oil', which is MoS2, It's not a cure all or HP booster but the lubricating properties are impressive. I've used this product for a number of years without any problems. Short of re-writing all the particulars, I suggest you look it up on the web.
molybdenum disulfide...........