Effects Of Zinc Oil Additives On Old Engines [Positive & Negative]

The classic car you drive now may need a zinc additive to let it run smoothly. Though the formulation of oil has changed, your ’80s car engine remains in the same place even in this era of modern technology.

It can’t move forward without zinc oil due to the design of your older car. In other words, modern oil can’t bring or make any difference in the performance of your old car. 

So, let’s take a look at the effects of zinc oil additives on old engines and why your car still needs high zinc oil

The Way Zinc Additives Function

Zinc is the short version of Zinc Dialkyl-Dithiophosphates. In other words, we know it as ZDDP. Also, people often call it ZDTP as it contains Zinc Dithiophosphates. 

When these two ingredients (ZDDP and ZDTP) are combined, they create a strong anti-wear film to provide the highest level of protection. 

Zinc additives work as lube by responding to the heat produced in the engine compartments. When the temperature rises, each of the metal components comes closer to the other. It may cause metal-to-metal friction. But zinc additives prevent it as it breaks down due to the high temperature and creates a chemical reaction. 

When you run your vehicle, every moving part of your engine starts rolling & sliding and comes closer to one another. During this time, zinc additives create an anti-wear film that sticks with those moving parts and prevents frictions. As a result, no damage occurs, and your engine runs smoothly. 

Most older car engines need more lubrication during engine warm-up, and zinc additives provide that level of lubrication. Indeed, zinc additives are a must for older car engines for superior engine protection against wear. 

3 Positive Effects Of Zinc Oil Additives On Old Engines

Motor oil containing zinc is crucial for old car engines or flat tappet engines. Here are the reasons why old engines like flat tappets need zinc oil and the benefits of using zinc additives in your old car.

1. Design To Protect Old-Engine

Older cars that were manufactured back in the ’80s had a camshaft design with a flat tappet engine. Due to the flat tappets, more friction is created. If you leave the flat tappets without any protection, it brings internal damage to your car engine.

But the zinc oil will help to prevent wear damage by lubricating every moving part of the engine. The zinc additives create a layer between metals and reduce friction to protect the engine. 

2. Reduce Friction

If you drive a car with a flat tappet engine, use ZDDP or diesel grade oil with zinc contents. Zinc works as lube. Many cam lobes and lifters get damaged because of using the wrong oil as the oil doesn’t provide the lubrication the old engine required.

But zinc additives lube every moving part, create an anti-wear layer, and reduce the friction. So, you don’t need to worry about the metal frictions as the zinc oil handles that. 

3. Improve Efficiency And Performance

Reducing friction means less pressure on your car engine. As a result, your car engine runs smoothly and boosts up overall fuel efficiency and engine performance. 

Negative Effects of Zinc Additives on Your Old Engine

The zinc additives don’t only improve the engine performance by protecting your car engine but also bring damages. 

1. Damage The Catalytic Converter

Zinc oil is pashed out mostly because it damages catalytic converters. When the valve opens, the zinc oil finds its way into the combustion chamber of your car engine. The zinc contained in the oil turns into ash before transferring through the exhaust pipe. 

Though most ash goes out through the exhaust pipe, some portion remains on the catalytic converters. Over time, it creates ash deposits and decreases the efficiency of catalytic converters. 

Therefore, phosphorus contained in the zinc oil also creates carbon build-up in the engine compartment. All of these reduce the lifespan of your engine. Consequently, you need to spend a leg and arm to repair or buy a new engine. 

But the heck is- your old car engine still needs zinc to protect it from the wear damage. So, what should you do to avoid the negative effects of zinc oil?

Simple, use top-quality zinc replacement additives. The additives get rid of zinc and phosphorus from the oil but provide the ultimate protection against wear. 


What does zinc additive do to engines?

The zinc creates an anti-wear coat and prevents metal friction to offer unsurpassed protection against wear. 

Why did they remove zinc from motor oil?

Zinc contains phosphorus, which creates carbon build-up in the engine compartment. Consequently, it damages your car engine. To avoid this, most oil manufacturers now remove zinc from motor oil. 

Do any oil additives really work?

No, oil additives don’t improve your engine efficiency. It is just engineered to mix with oil. 


Zinc oil additive has both upsides and downsides. The plus of zinc oil is your older car engine needs it badly to avoid the most adverse situation. It protects your car engine from high temperatures and damages by lubricating the moving parts.

But the downside is- the phosphorus contained in the zinc oil builds carbon deposits in the engine compartment. Consequently, it damages the catalytic converters and reduces the longevity of your car engine. 

To sum up, the effect of zinc oil additives on old engines is positive and negative. 

To avoid the negative sides, we recommend you use zinc replacement additives. They offer ultimate wear protection without the negative impacts of zinc oil. 

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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