ZDDP Stands for Zinc Dialkyldithiophosphate – It is An Anti-Wear Additive Used in Motor Oil that Contains Zinc and Phosphorus to Provide Wear Protection for Classic Car, High-Performance and Racing Engines with Flat Tappet Camshafts
Both engine technology and oil technology have evolved over the years. Today’s performance engines have very different oil requirements compared to older engine designs from the 1960s and 1970s. The most commonly used anti-wear additive in motor oils is zinc dialkyldithiophosphate (ZDDP). Older engines equipped with flat-tappet camshafts require higher levels of ZDDP than today’s engines. Since the amount of ZDDP in oils formulated for today’s automobiles has been greatly reduced and newer API oils are not designed specifically for older-style, modified engines, engine wear can be a major issue. Therefore, AMSOIL manufactures high ZDDP oil tailored to meet the specific needs of a variety of vehicles. Whether you’re a classic car enthusiast, hot rodder, tuner or drifter, your equipment will benefit from the protection provided by these high ZDDP motor oils.
Demands on Motor Oil are Escalating
As today’s automotive engines push the envelope seeking higher fuel economy and lower emissions, the demands placed on motor oil are escalating. More stress is being put on engine components and the oil must protect parts from wear, even as they are pushed beyond the limits of vehicle manufacturers’ design. This is where the most recognized anti-wear additive, ZDDP, comes into the play. ZDDP is very good at reducing wear and improving oxidation stability. It also offers mild extreme-pressure (EP) protection.
All engines benefit from oils with superior film strength and anti-wear properties, so why don’t all motor oils have boosted levels of ZDDP? It’s back to the goal of improving emissions systems performance. Generally, ZDDP used in high levels results in volatile phosphorus being transferred from the combustion chamber to the catalytic converter, making the catalytic converter less efficient in turning carbon monoxide (CO) into carbon dioxide (CO2). The EPA mandates that catalytic converters operate as designed for more than 100,000 miles. As a result, ZDDP additive levels are now limited for newer motor oil specifications.
Phosphorus in Motor Oil
The American Petroleum Institute (API) and International Lubricants Standards Approval Committee (ILSAC) have mandated the reduction of phosphorus to extend catalytic converter life. Current API SN and ILSAC GF-5 specifications for gasoline engines have maximum and minimum phosphorus levels of 800 ppm and 600 ppm, respectively, for SAE 0w20, SAE 5w20, SAE 0w30, SAE 5w30 and SAE 10w30 motor oils.
The largest portion of the volatile phosphorus is generated right after you change your oil. So the more you change your oil, the more your catalytic converter is exposed to this volatile phosphorus. Conversely, longer drain intervals can limit the negative impact of volatile phosphorus on catalytic converters.
Flat Tappet Camshafts and Higher Spring Pressure
Phosphorus levels in motor oil have been reduced to preserve catalytic converter life, but concerns have risen that oils containing lower levels of zinc and phosphorus could provide insufficient protection in high-pressure areas of flat tappets and camshaft lobes found in many classic car and high performance engines.
ZDDP contains both zinc and phosphorus components that work together to provide anti-wear protection and minimize lubricant breakdown. Specifically, ZDDP helps protect high-impact surfaces like camshaft lobes, lifter surfaces and rockers against wear. As temperatures rise and surfaces come closer together, ZDDP decomposes and the resulting chemistry is what protects the critical metal surfaces. When parts move during operation, any sliding or rolling motion takes place on top of or within the ZDDP anti-wear film, which reduces metal-to-metal contact. This is especially important in modified engines with flat-tappet camshafts because the engine is creating more horsepower than it was designed for, which puts more stress on the engine. The camshaft and lifters are responsible for triggering the precisely tuned movements of the valvetrain. Without the protective film barrier provided by ZDDP, the cams and lifters will wear from the force of operation, resulting in poor performance.
All engines, especially high-performance modified racing engines, benefit from oils with superior film strength and anti-wear properties. The flat tappet/camshaft lobe interface is the one area in an engine that has extreme contact load. Since this load increases significantly when non-stock, high-pressure valve springs are used, the use of properly formulated motor oils is extremely important to reduce wear and extend flat tappet and camshaft life, especially during the critical break-in period.
AMSOIL Break-In Oil is specifically formulated with zinc and phosphorus anti-wear additives to protect cam lobes, lifters and rockers during the break-in period. Break-in duration varies between engines; follow the engine builder’s or manufacturer’s recommendations. Once the break-in phase is completed, the AMSOIL synthetic motor oils listed below, which are formulated with high levels of zinc and phosphorus, will provide premium protection to flat tappet cams.
Demand for High ZDDP Motor Oils
Many enthusiasts and engine builders are seeking out high-ZDDP specialty oils and AMSOIL is supplying their demand. The following tables list many of the AMSOIL synthetic motor oils that are formulated with high levels of ZDDP anti-wear additives. Also listed is how much zinc and phosphorus each motor oil contains. Links to each of these products is provided below, under the Applications heading.
Note: Some motorists think that increased zinc content equals increased wear protection, but the mere presence of zinc doesn’t mean it is in the form of ZDDP. In other forms, zinc offers additional oxidation protection but little wear protection. There are also other factors that influence an oil’s ability to control wear, such as base stocks. Therefore, the greatest concern should be in using a properly formulated, well-balanced oil designed for its intended application.
AMSOIL Break-In Oil is a 30-weight viscosity grade oil formulated without friction modifiers to allow quick and efficient piston ring seating in new and rebuilt high-performance and racing engines. It contains zinc and phosphorus anti-wear additives to protect cam lobes, lifters and rockers during the critical break-in period when wear rates are highest.
AMSOIL Z-Rod 10w30 and 20w50 Synthetic Motor Oils are formulated with high zinc and phosphorus levels to provide superior protection in gasoline engines with flat-tappet camshafts, particularly older and modified engines. Z-Rod also contains high levels of rust and corrosion inhibitors for maximum protection during long periods of storage.
AMSOIL Premium Protection 10w40 and 20w50 Synthetic Motor Oils are formulated with high zinc and phosphorus levels to provide outstanding protection in both gasoline (SL) and diesel (CI-4 Plus) applications. They are an outstanding choice where high zinc-containing protection is required, such as late-model hot rods that require extra camshaft protection.
AMSOIL Series 3000 5w30 Synthetic Heavy-Duty Diesel Oil is a combination diesel/gasoline oil with a higher starting TBN to handle the significant stresses from high soot-loading and acid generation in modern diesel engines. It contains the high phosphorus and zinc required for long-life engine protection.
AMSOIL 15w40 Synthetic Heavy-Duty Diesel and Marine Motor Oil is engineered for use in a wide variety of light- and heavy-duty applications. It is formulated with high levels of zinc and phosphorus to ensure protection of flat-tappet camshaft lobes in high-performance diesel engines.
AMSOIL Dominator 5w20, 10w30, 15w50 and SAE 60 Synthetic Racing Oils are all formulated with the same robust additive package, but more for true racing applications. This makes it the right choice for muscle cars, street rods and other high-performance vehicles with flat-tappet camshafts.
Visit our Synthetic Racing Oil Comparison page to see how other brand names of racing oils rank for wear protection in comparison to AMSOIL!
Reference: AMSOIL, Inc. Flat Tappet and Camshaft Lobe Lubrication Bulletin (67 kb pdf) outlines the lubrication requirements of flat-tappet camshaft engines and the importance of high ZDDP motor oils in these engines.