zinc oil additive is an anti-wear agent that's especially useful for older engines. This is because they typically run at high speeds, so they need an additive that can withstand that pressure.

The best zinc oil additives provide a thin, durable, and flexible film of protection that helps to reduce friction between metal-to-metal lubrication points in the engine. When these two surfaces come into contact, they're exposed to a momentary increase in temperature, which causes them to form a temporary lubricant film that will help them to glide smoothly.

Older engines, including performance vehicles with flat tappet camshafts, need a zinc oil additive to protect the lifters and camshaft from wear that can occur at high engine speed. Luckily, there are several motor oils on the market that have formulated a specialized zinc replacement additive to provide this kind of protection.

When choosing an oil for your old car or hot rod, you'll need to look for a ZDDP level of between 1,000 ppm and 1,400 ppm and phosphorous content of similar levels as well. These are both important for ensuring that your classic vehicle stays protected during break-in and regular use.

Why Zinc is No Longer an Additive

Over the past 10 years, the industry has gradually phased out the addition of zinc and phosphorous in most engine oils because these compounds can cause carbon buildup and premature catalytic converter failure. The phosphorous in these additives also creates a bond with the mesh coating on catalytic converters, making them less effective at burning off contaminants.