Drivers who own a classic car, or any vehicle with an older engine built in the mid-1980s may have heard of the need for zinc dialkyldithiophosphate (ZDDP) in its motor oil. Today, some argue that ZDDP is essential in motor oil while others claim that modern oils are good enough. The question is, do older engines need a zinc additive or is it just an additional expense that can be foregone?
The answer is Yes! You need zinc especially if your engine has a flat tappet camshaft, but if your engine has a roller camshaft then it’s not important.
What is ZDDP and Why was it Added in Older Oils?
ZDDP is a combination of zinc and phosphorus that acts as an anti-wear additive in motor oil. It provides a protective layer between metal parts, which are constantly under high pressure, thus helping to reduce friction and prevent premature wear.
In older engines, especially those with flat tappet camshafts, metal parts are usually in high-pressure contact because of cam lobes and lifters rubbing against each other. These parts could wear easily if there was no protection, leading to poor performance or even failure.
ZDDP was a standard ingredient in motor oils for decades, ensuring that engines lasted long, but this changed as automotive technology advanced.
Why Zinc is No Longer an Ingredient in Moto Oils?
Zinc is no longer added to motor oils because of emission regulations. Additionally, high levels of zinc in motor oils were found to cause harm to catalytic converters in modern cars. As most engines switched to roller camshafts, which do not need as much ZDDP, oil manufacturers found it necessary to reduce zinc content in oils to adhere to emission regulations.
Modern oils also lack zinc because modern engines have evolved. Therefore, to meet these changing engine designs, zinc has been eliminated. However, the decrease in ZDDP levels means that modern oils don’t offer the protection that older engines rely on.
Does Your Engine Need ZDDP?
As stated earlier, your engine would only need ZDDP if it has a flat tappet camshaft. When an engine with a flat tappet camshaft gets to a high speed, friction between the lobes and followers creates pressure which squeezes out motor oil. The loss of oil can cause damage and that’s where the need for anti-wear additives comes into play.
If your engine has a roller camshaft, which is common in older engines from the late 1980s onwards, then you do not need extra zinc. However, if you have a high-performance classic engine regardless of whether it has a flat tappet or a roller camshaft, it would be advisable to add ZDDP to protect it from wear.
Where to Get Zinc for Your Engine.
The first option is to add a bottle of ZDDP to your oil during an oil change. The second option is to buy high-zinc motor oil, especially the specialty oils used in classic and racing cars. Lastly, use diesel oil, but before doing that, always check if it is compatible if you plan to use it in a gasoline engine. Zinc additives are easy to find at an auto parts store, and also affordable, therefore it would be wise to add them to your engine for long-term protection and performance.
Finally, it is important to note that high-zinc oils are only recommended in older and high-performance engines. Therefore, if you have a modern car, using these oils could be harmful to catalytic converters that reduce airborne pollutants being emitted by the engine.