Zinc is a common metallic element used for many different applications in machinery and construction. The metal has certain properties that make it resistant to the corrosion that iron suffers from, so it is used to coat many different steel products in a process known as galvanizing. These same properties make zinc a valuable additive in motor oil formulas as long as it is used in the proper amounts.
The purpose of motor oil is to lengthen the life of the engine. Engines contain many moving parts that work together very quickly to produce energy. On their own, these components would build up a large amount of heat and quickly wear the engine out through friction. Motor oil flows through the engine to disperse the heat and lubricate moving parts, reducing friction and the damage it causes.
Motor oils have many different ingredients, which is one reason there are so many choices available. Several different types of oil are often used, and other chemical compounds known as additives are included. These extra elements are designed to give the oil certain qualities that make it less viscous or less flammable, or add other useful qualities. Zinc is one of these additives.
In motor oil, small amounts of zinc are included to help the engine reduce wear caused by metal to metal contact within the engine. Motor oil and engine construction are designed to prevent this type of contact, but if they fail then zinc compounds step in and provide an emergency buffer to protect the metal from suffering as much damage as it normally would.
Zinc levels in motor oil range depending on the oil and its application. As of 2010, American Petroleum Institute regulations limit zinc levels to 0.08 percent of motor oil content (down from the previous 0.15 percent). This low amount is regulated because zinc tends to combust poorly and has an unhealthy effect on catalytic converters and emission systems.
While anti-wear additives are important in motor oil, different oils have different amounts of both zinc and phosphorous, which both help protect engines from metal wear. In vehicles that are used at relatively low speeds and are not pushed hard, low zinc levels are a good idea. Higher zinc levels apply more to air-cooled motorcycles or turbocharged cars that often need the extra protection.
