As REV X ZINC Oil Additive (ZDDP) is heated, it creates a film that coats the engine parts with an anti-wear layer. Think of it as a sacrificial layer that will wear away, preventing the wear on your vital engine parts. ZINC is very beneficial for flat tappet motors, which have a flat lifter, as the name suggests. When the engine runs, the cam lobe is in constant contact with the tappet's flat surface. Simultaneously, this creates high temperatures due to the friction between the two. If the protective film produced by the ZDDP were not present, this heat and friction would wear away at the lifters and cam, leading to engine failure.
You can use it with any lubricant where heat and friction are present, such as steering boxes, manual transmissions, differentials, and even transfer cases. With that in mind, the zinc oil additive only adds an anti-wear layer. Suppose you want to reduce friction, lower component temperatures, and clean your entire oil system.