Zinc Additives in Oil and How It Helps

Recently, Zinc has become even more important in the car community, mostly because of the old adage, “you don’t know what you got 'til it’s gone.”

Zinc was often over-looked in terms of its importance in many engines. If you browse the oil additives section at AutoZone, you'll notice Zinc called out on several items.

What is Zinc, anyway?

Zinc is the only element that starts with Z, and it’s a vitamin listed on food packaging, which are the two things that make it the most famous. It’s also used to fight corrosion, as a galvanizing agent, is critical to create brass, and shows up in thousands of compounds that affect your everyday life. Check out the Zinc wiki page with 270+ sources to read up on all that.

We’re here to talk about motor oil.

What does Zinc have to do with motor oil?

“Zinc” in motor oil usually is describing a compound called Zinc Dialkyl Dithiophosphates or ZDDP. According to Valvoline, “its primary role is to prevent metal-to-metal contact between engine parts by forming a protective film. Despite being referred to as zinc, ZDDP also contains phosphorus, which helps to perform the anti-wear function in the motor oil.”

Zinc acts as a friction inhibitor, and research suggests that older engines using “flat tappet” lifters in the engine (pretty much any V6 or V8 older than 1988) need to have zinc present in the engine oil in order to keep the camshaft and lifters from wearing prematurely.

So why isn’t Zinc or ZDDP in modern motor oil?

Herein lies the problem. About 10 years ago, it was also discovered that in general oil consumption, Zinc, especially the phosphorus present in ZDDP, is a primary cause of premature catalytic converter failure. With the government setting mandates on manufacturers covering the service life of catalytic converters over 100,000 miles, this caused nearly every oil manufacturer over the last 10 years to slowly remove zinc from the ingredients in their oil. Diesel oils soon followed suit, until today, no oil that is approved for on-road use contains Zinc. This of course doesn’t affect newer engines with roller lifters or overhead cams at all – but for older engines – it limits the options for oils with ZDDP.

Currently, very few oils on the market contain zinc – and all of these are designated as “off-road” oils, such as Valvoline racing oil. However, if you’re looking to add Zinc, there are of Zinc additives, that, when coupled with your favorite oil, provide the protection you need.

For starters, STP oil treatment, that little blue bottle you might have seen on AutoZone shelves, contains a considerable amount of Zinc necessary for an older engine. Two other more recent additions in many stores are the Hy-per lube Zinc additive, and Lucas engine break-in oil additive, which contains a massive amount of zinc. Read over any additive’s ingredients, and if you don’t see Zinc, it’s probably not in there.

Zinc is not only critical for older flat-tappet engines, but many argue it’s critical for new engine break-in. An engine’s break in period is critical for its long-term success, as everything from main and rod bearings, to rings, cams and oil pump are getting adjusted to their new life. Remember, if you have an older vehicle, whether it’s a 1966 Mustang or a 1979 Ford pickup, it’s a good idea to put zinc into the oil.

More on Synthetic and Conventional Oil

Need Zinc additive or oil advice? Shop for oil and additives at or stop into the OilZone at AutoZone.

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