Zinc Dialkyldithiphosphate Provides Proven Wear Protection

But its incompatibility with pollution-reduction devices severely limits its use in modern motor oils.

As today's automotive engines push the envelope seeking higher fuel economy and lower emissions, the demands placed on motor oil are escalating. This push for improved performance is nothing new. Racers and muscle-car owners have long looked for ways to squeeze more horsepower from their vehicles. This is often done in vintage cars by modifying the engine, while tuner enthusiasts usually focus on computercontrolled performance improvements. Whatever your preferred method, it puts more stress on engine components, and the oil must protect parts from wear even as they are pushed beyond the limits of OEM design. This is where the most recognized anti-wear additive, zinc dialkyldithiophosphate (ZDDP), comes into the picture.

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ZDDP is very good at reducing wear and improving oxidation stability. It also exhibits mild extreme-pressure (EP) protection. ZDDP contains both zinc and phosphorus components that work together to provide anti-wear protection and minimize lubricant breakdown. Specifically, ZDDP helps protect highimpact 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 benefit from oils with superior film strength and antiwear 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. Like with lead in 1970s gasoline, phosphorus can blind over the catalytic reaction sites in the converter, making it 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 levels are now limited for newer motor oil specifications. 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.

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. Many new engines use roller cams, which aren't as sensitive to ZDDP anti-wear protection as older flat-tappet camshafts and solid lifters. Older engines equipped with flat-tappet cams require higher levels of anti-wear/mild EP (ZDDP) than today's engines. This area in an engine is exposed to 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. Since the amount of zinc and phosphorus 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.

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AMSOIL manufactures a complete line of motor oils tailored to meet the specific needs of classic cars and other vehicles requiring higher anti-wear/mild EP protection. AMSOIL Z-ROD® 10W-30 Synthetic Motor Oil (ZRT) & AMSOIL Z-Rod® 20W-50 Synthetic Motot Oil (ZRF) are designed with the level of anti-wear/mild EP required to safely protect older and modified engine designs such as those with flat-tappet camshafts. It is also designed specifically to resist rust and corrosion that attacks engines during periods of inactivity and storage. AMSOIL DOMINATOR® Synthetic Motor Oil (RD20, RD30, RD50,RD60) is formulated similarly, 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. AMSOIL Break-In Oil (BRK) is designed to work quickly in new and rebuilt high-performance and racing engines. This SAE 30 viscosity grade oil features a no-friction-modifier formula that helps induce controlled wear in rings to help mate and seat piston rings. It also has very high levels of ZDDP.

Whether you're a classic-car enthusiast, hot rodder, tuner or drifter, your equipment may require the protection provided by these products. Knowledge is power; but we want you to experience maximum power from your engine also!

Solving the Challenges of Flat-Tappet Cams in Classic Car Engines

Summer belongs to classic cars and hot rods. It's the season when thousands visit car shows across North America and loyalists of every make and model cruise the streets to show off their rides. One of the big concerns among classic car owners in recent years, however, has been the abundance of flat-tappet camshaft failures that many attribute to the reduction of zinc and phosphorus in today's oil formulations.

Zinc dialkyldithiophosphate (ZDDP) is the most common zinc-based additive, and is used primarily as an anti-wear agent to prevent premature engine wear. It also provides corrosion and oxidation protection. However, because the zinc and phosphorus found in ZDDP can negatively affect catalytic converters, it has been phased out of motor oil formulations in recent years.
Reducing ZDDP content has drawbacks, as classic car owners have found. Older vehicles with flat tappet camshafts and, in particular, engines that include high-tension valve springs or other modifications that create high contact pressures can suffer premature wear due to reduced ZDDP levels.

Flat-Tappet vs. Roller Cams

The design of flat tappet cams makes them especially vulnerable to wear. As the name indicates, the tappet - or lifter - is flat. During operation, the surface of the cam lobe slides rapidly over the surface of the tappet, producing high friction and temperatures. A thin oil film is the only barrier that prevents the lifter and cam lobe from welding together. If the oil film fails or provides insufficient wear protection, the two components can eventually wear the flat tappet cam and affect valve operation. Engine power and efficiency can decline if the flat tappet cam cannot lift the valves enough to adequately charge the chamber for ignition or release exhaust fumes. Because most V8 engines of the muscle-car era came standard with flat tappet cams, the problem is especially prevalent to classic-car and hot-rod owners.
Roller cams, on the other hand, are differentiated by rolling contact rather than sliding contact. Although more costly, roller cams are common in most modern vehicles and can be retrofitted into classic-car and hot-rod engines.

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Demand for High-Zinc Oils

The abundance of flat tappet camshaft failures in classic-car and hot-rod circles has spurred the market for high zinc motor oils formulated especially to protect flat tappet cams AMSOIL Z-ROD® 20W-50 Synthetic Motor Oil (ZRT) and AMSOIL Z-ROD® 10W-30 Synthetic Motor Oil (ZRF) are specially engineered for these classic and high-performance vehicles. It features a high-zinc formulation to help prevent wear on flat tappet cams and other critical engine components. Because many of these vehicles sit idle much of the time, Z-ROD contains a proprietary blend of rust and corrosion inhibitors for added protection during longterm storage. Z-ROD Synthetic Motor Oil is designed to perform on the street and protect during storage.

Complete Vehicle Protection

Classic cars and hot rods need more than just premium engine protection. Many are modified to deliver increased power and torque, placing added stress on the transmission, differential and chassis. AMSOIL Synthetic Manual Transmission & Transaxle Gear Lube (MTG), Severe Gear® Synthetic Gear Lube (SVG, SVT, SVO & Dominator® Synthetic Racing Grease (GRG) offer advanced protection modified classic cars and hot rods need. These and other products are featured in the new Classic Cars Brochure (G3113).

Purchase AMSOIL products at up to 25% discounted as an AMSOIL Preferred Customer.