What is the Effect of ZDDP on my Vintage or Classic Vehicle?

What is ZDDP?

Developed during the early 1940s, Zinc Dialkyl Dithiophosphate (ZDDP) was the original engine oil multi-functional additive that provided anti-wear, anti-corrosion, anti-oxidant, and mild extreme pressure (EP) performance. It provides a chemical protective film on metal parts and is ideally suited to protect high-load contact points such as camshaft lobes, followers, and other areas of the engine where metal-to-metal contact is prevalent.

Why is it important for vintage and classic engines?

Whilst modern engines have developed alternative ways, in classic engines especially, it is absolutely critical that anti-wear additives are working to protect the engine’s moving components. Without the correct amount of ZDDP, and because of how important these components are, the engine can experience premature wear and may run poorly.

How much is the ‘correct’ amount?

Millers Oils recommends an optimum amount between 1000 – 1400 ppm of ZDDP. Too little won’t offer enough anti-wear protection. Too much will not provide increased levels of protection, but rather actually create friction, and increase wear due to the ‘over-plating’ of components. In addition, high levels of ZDDP in an oil can harm emission control devices such as catalytic converters.

Does having Zinc present means it is ZDDP?

Zinc doesn’t mean ZDDP. Pure Zinc does not contribute to anti-wear protection. The anti-wear part of ZDDP is done by the Phosphorus component of the additive.

Shall I just buy an engine oil with as much ZDDP as possible?

We wouldn’t recommend just buying an engine oil with the most ZDDP you can find. All Millers Oils classic engine oils are formulated with the optimised amount. It is important to note that a product with 1400 ppm ZDDP is not necessarily better, as the level has to be balanced with other additives in the formulation to ensure all-round performance.

Read our blog about whether synthetic oils are safe for classic vehicles here. 

Click here to find out more about our vintage and classic range.

Our in-house Technical Support team are always happy to discuss any further questions you have. Give them a call: 01484 475060

Or email: technical@millersoils.co.uk