motor oil with zinc is a vital ingredient in many older car engines. These additives help prevent metal-to-metal contact in camshafts and other engine parts by forming a protective film. While most modern cars no longer need this heavy-duty protection, classic and hot rods do. Zinc additives are also a great choice for breaking in new engine components, as they provide more lubrication than regular street oil during that critical start-up period.

When most people talk about "zinc in the oil," they are actually referring to zinc dialkyl dithiophosphates or ZDDP, an anti-wear additive. It's often paired with phosphorous, and together they form an effective coating that reduces friction between moving parts in an engine. These ingredients are commonly used in racing and high-performance automotive oils. Most regular API oil blends contain limited amounts of these ingredients due to EPA and OEM restrictions.

The main reason that most flat tappet cam engines need zinc or a similar additive in their oil is that these camshafts tend to press down on the lobes of the cam and then roll or slide across them to open valves. This action causes intense pressure and can wear down the camshaft and lifters faster than they should. Zinc additives help protect these metal parts by bonding to them and forming an anti-wear layer that resists this extreme strain. In addition to providing better lubrication, this zinc-phosphorous coating also protects against corrosion and other damage.