In recent years there has been a growing incidence of premature cam/tappet failures on pre-cat/pre-OBD engines. Unsurprisingly these failures were commonly attributed to poor quality components, bad engine building, adverse operating conditions or ‘cheap’ oil – to name the four most popular explanations. Although some of the failures may well have been due to one or more of these four possibilities, there was increasing concern among professional engine builders that some other factor was at play.
The missing factor was eventually identified as ZDDP (Zinc Dialkyl Dithiophosphate), an essential EP (extreme pressure) engine oil ingredient. When car manufacturers introduced on board diagnostics (OBD) with catalytic converters to control engine emissions, ZDDP in oils was found to reduce the lifespan and effectiveness of the cats. The result was a drastic reduction in the concentration of ZDDP and a new generation of engines to comply with these tough emission laws.
In March 2006 the American Engine Rebuilders Association (AERA) circulated a bulletin (TB2333) which formerly identified the absence of sufficient ZDDP additive in modern engine oils with cam/tappet failures on pre OBD engines (generally pre- 1990). It was recognised that some specialist oils do have the higher levels of ZDDP which conform to the original API ‘SF’ classification but such oils were niche market and not generally available. Even with some of these specialist oils the levels of ZDDP varied with few, if any, having the optimum concentration of between 0.18% - 0.20%.
ZDDPlus was subsequently formulated in the USA to restore optimum levels of ZDDP additive to any type of quality engine oil, mineral or synthetic and regardless of viscosity. ZDDP additive for all pre OBD engines has now been universally endorsed by the performance cam suppliers including Isky, Erson, Crower and Delta. ZDDPlus is not being trumpeted as a magic formula.
ZDDPlus is simply an exact replacement to the EP additives no longer found in modern oils yet essential to protect your classic car engine from premature wear and an expensive rebuild. One 4oz bottle is sufficient to treat an average size sump capacity of 4.5 – 5.5 litres.
- Additional Information
Part No ZDDPLUS Product Group Additives: Petrol & Oil Stock Status No Longer Available
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