Does Diesel Oil Have Zinc [Explained]

Zinc is an important additive in engine oils as it minimizes engine wear and tear. If you have a diesel engine, you’d have to use diesel oil. It’s normal to be worried about the safety of your engine if your diesel oil lacks zinc. So, does diesel oil have zinc?

The short answer is YES, most diesel oils have zinc additives in them. Even though the quantity of zinc has been reduced over the years, there’s still sufficient zinc in most diesel brands.

does diesel oil have zinc

However, you should only use diesel oil in diesel engines. There’s a common misconception that diesel oil is the right choice for classic cars and hot rods. But that’s not true. Keep on reading to find out more about it in detail.

Does Diesel Oil Have Zinc [All You Need To Know]

Diesel oil is one of the many types of petroleum-based fuel that’s made to be used in diesel engines. They’re similar to gasoline fuels up to a large extent. Both of them are made by adding additives to the base oil.

One such additive is zinc. Diesel oils also have variations in their formulas. When it comes to diesel oil for motors, most of them will have zinc. You’ll have to find out for yourself how much zinc is in a specific diesel oil. That’s because different brands may have different levels of zinc in their oils.

diesel oil

It’s not hard to get an estimate of how much zinc there is a diesel oil. All you’ll have to do is look at the API rating of the oil. If a diesel oil has an API rating rate of CI-4, CI-4 Plus, or CJ-4, it usually has a zinc level of around 1100 ppm.

A common misconception these days is that diesel oil is the right oil to use in gasoline flat-tappet engines. But that’s not the case. The right oil for your gasoline engine needs to have the right level of ZDDP protection. It’ll get a little clearer after you look at the numbers.

Flat-tappet gasoline engines usually require 1200 to 1300 ppm of Zinc in the oil for good protection. Similarly, muscles and hot rods require around 1600 ppm of Zinc.

flat tappet engine cars

There are many gasoline oils that don’t have such high amounts of zinc. But there’s more opportunity to add ZDDP to them. So, once you supplement the oil with the right zinc additive, you’ll have the perfect combination.

You won’t be able to add a lot of ZDDP in diesel oils as they’re highly concentrated. They have high levels of detergent and dispersant additives. So, there’s not much room to add more additives. Keep on reading if you want to find out more about why diesel or racing oil isn’t the right choice for classic cars.

Is Using Zinc In Oil A Myth?

The use of zinc in motor oil can be traced back to the 1940s. It was around that time that zinc was incorporated into motor oils for its anti-wear protection. You’d see a “Zinc” or “Phosphorus” marking on an oil label if it has zinc.

The zinc additive used in motor oil is called zinc dialkyl dithiophosphate or ZDDP. And yes, it was mainly used to prevent engine wear, especially in flat tappet engines where the camshaft contacted the lifter.

During the 1950s, a very low level of Zinc was added to engine oils. Generally, motor oils around that time had about 300 ppm of ZDDP. However, due to its anti-wear properties, the concentration of zinc kept being increased. The level of zinc reached 1200 to 1400 ppm when it was at a maximum in the 1980s.

The funny thing is that such a high amount of zinc increased the engine wear as opposed to reducing it. So, hot rodders and car enthusiasts so many issues during the 1990s and early 200s. Camshaft and lifter failures became much more frequent during that time.

Such a high amount of Zinc also made the catalytic converters in gasoline engines less effective as they got coated with Phosphate. So, the amount of ZDDP was reduced and it dropped to 600 to 800 ppm in engine oils.

Why Use High Zinc Motor Oil?

The main use of Zinc dialkyl dithiophosphate or ZDDP in motor oil is to protect the engine from wearing out. It works by creating a surface-level boundary on the engine. As Zinc sticks to the metal, it reduces the metal-to-metal contact when there’s too much load on the engine.

why use high zinc motor oil

Besides that, the presence of zinc also prevents the engine from being corroded. Due to Zinc, oxidation takes place, and the engine remains free from the formation of rust.

Due to these unique advantages, it’s a good idea to use a high-zinc oil. But make sure you follow the manufacturer’s guidelines when it comes to selecting the right oil for your car. You can use additional ZDDP for more engine protection but don’t overdo it too much as it can have an adverse effect.

Is Diesel Oil Or Racing Oil Ideal For Classic Cars?

A common question I often get is what’s the right type of oil for classic cars. Yes, I am talking in terms of stopping cam wear on the flat tappet engines. So, is racing oil or diesel oil the right choice for these cars?

Generally speaking, most diesel oil brands put sufficient zinc in the oils. However, that doesn’t mean it’s the ideal choice for classic cars. Let me explain why you should always pick high-zinc oil compared to racing oil.

classic car

In a regular high zinc oil, there’s a lot of room for additives. But racing oil is made a certain way and there’s less room for additives in them. Besides, they were made with racing requirements in mind. They’re not the ideal choice for regular use.

About using zinc in oil, Rislone says, “If your older vehicle has an engine that uses a flat tappet lifter, it will need to have zinc or a zinc replacement additive in its engine oil. Having zinc in the engine oil will prevent the lifters and camshaft from wearing down prematurely.

On the surface, it could seem like racing oil is the right choice for a classic car. It’s true that the performance of your car will instantly seem smoother if you use diesel oil. So, why do I recommend missing out on that?

Firstly, because it won’t last forever. The additional performance comes at a cost. Using such oil will leave more deposits on your car. Such oils aren’t meant to be stored in your car. You’ll have to consume them in a short period. 

With that said, here are a few other instances in which you should avoid using racing oil in your car:

01. Running Into Traffic

Racing vehicles go on a specific track free from oncoming traffic. But the same can’t be said if you drive your car in a city. The oil will have to be blended for fuel dilution and oxidation from the PCV. Racing oil isn’t compatible with this fuel dilution and that’s why they’re not the ideal choice.

02. Temperature Fluctuations

Another reason to not choose racing oil is its inability to adapt to cold weather. If the temperature gets lower than 60 degrees Fahrenheit, racing oil won’t be able to handle the condensation.

It simply doesn’t have the additives that are required to tackle the condensation and the possible foaming. The acids that are created lead to more deposits and leads to engine wear.

03. Absence Of Rust Inhibitors

The fact that rust inhibitors aren’t present in racing oil is often overlooked. But this is a big deal. Especially, when it comes to the classic cars. You’ll be surprised to know that rust and corrosion do more damage to such engines than startup wear.

Racing oils also lack seal swellers. However, you’ll find them in diesel oil. But if you use a high quality, you also get the added benefit of rust inhibitors. Racing oil isn’t also meant to protect the engine from deposits. However, a high-quality zinc oil will take that into account and minimize the deposits.

So, you can go for a synthetic motor oil to avoid these issues even for engines with flat tappet cams. Similarly, a synthetic motor oil with high zinc additives will perform much better and is really the ideal choice for classic cars.

How Does Diesel Oil Differ From Gasoline Oil?

The composition and use case of diesel oil and gasoline oil isn’t the same. There are some key differences between them. Let’s take a quick look at them.

01. Viscosity Modifier Polymers

There are polymers used in multi-viscosity oils. They are oils that have different viscosity at different operating temperatures. These viscosity modifier polymers are different for diesel and gasoline oils.

It’s because of the type of operation they require. Diesel engines have a low RPM range and they need polymers that are stable to protect the bearings. But gasoline oils provide a much better range of RPM. So, they need polymers that have thickening efficiency capability and shear stability to protect the engine.

Besides, diesel oil generally has a higher viscosity than gasoline oil. Putting diesel oil in gasoline engines will create several problems. For example, the oil would be thick during cold starts and it’ll be hard to circulate it to different engine components.

02. Additive Levels

Diesel oils have a much higher number of additives per volume compared to gasoline oils. There are many detergent additives in diesel oil as diesel engines tend to create much more soot. The detergent in the oil helps to clean the engine clean despite the formation of soot.

Besides, the ZDDP used in diesel oils is primary ZDDP and it gets activated at higher temperatures. However, the ZDDP used in gasoline oils are both primary and secondary ZDDP. So, they become active at much lower temperatures. That’s required for gasoline engines as they experience more cold starts.

03. Catalytic Converter Efficiency

The catalytic converter is a crucial engine component that reduces the toxic emissions coming out of the vehicle. It breaks the emission into less harmful gases before letting them out into the atmosphere.

catalytic converter

But zinc and phosphorus are elements that can reduce the efficiency of catalytic converters. Gasoline oils usually have a much lower concentration of zinc and won’t have an adverse effect on the catalytic converter. And that’s one of the main differences between these two types of oil.

The catalytic converters on diesel systems can somewhat counter this issue as their engines are built that way. But you can’t put diesel oil in gasoline engines without the oil damaging the catalytic converter.


Does diesel oil have zinc? Now, you know that both diesel and gasoline oils have zinc additives in them. You can even add a little zinc additive on your own for extra protection of your engine.

But don’t add too much as you should already be aware that it can also damage the engine. Ideally, you should follow your car manufacturer’s advice when it comes to these things. Check out our guide on the top zinc motor oil companies if you’re interested.

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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