The new Z-ROD 10W-40 Synthetic Motor Oil (ZRD) provides the rock-solid wear protection for flat-tappet cams and against rust during storage.

Classic Cars Have Different Needs

Oil formulations have evolved over the years along with the evolution of engine design. Use of modern emissions-regulation devices has resulted in reduced zinc dialkyldithiophosphate (ZDDP) content in motor oil. High amounts of phosphorus in ZDDP additives can negatively affect a vehicle’s catalytic converter and reduce its effectiveness. However, ZDDP additives are proven anti-wear agents that are especially important in modified, classic and performance vehicles that feature flat-tappet camshafts and custom lifters and rocker arms for increased performance. The limitation of these additives in modern oils reduces their effectiveness in classic and performance cars.

Protecting Flat-Tappet Cams

Two main types of camshafts are used in automotive applications: flat-tappet and roller. The tappet, or lifter, on the flat-tappet camshaft is flat and requires an oil film to keep its surface separated from the cam lobe. Flat-tappet camshafts produce high friction (high heat) because the surfaces slide rapidly against each other. The oil film is the only barrier that prevents the lifter and cam lobe from welding together.

The friction between the two components can eventually wear down the flat-tappet cam and affect valve operation. Engine power and efficiency decline if the flat tappet cams can’t lift the valves enough to adequately charge the chamber for ignition or to release exhaust fumes. These areas are splash-lubricated rather than pressure lubricated like other areas of the engine, placing extra strain on anti-wear additives.

Roller cams, on the other hand, are differentiated by rolling contact rather than sliding contact. Although more expensive, roller cams are common in most modern vehicles and can be retrofitted into classic-car and hot-rod engines.

Z-ROD is Packed with ZDDP (Zinc)

AMSOIL Z-ROD Synthetic Motor Oil is formulated with high levels of ZDDP to protect flat-tappet cams, lifters, rockers and other areas susceptible to wear. Its high-zinc, high-phosphorus formulation provides the extra wear protection these critical splash-lubricated components require.

Long-Term Protection from Rust & Corrosion

Rust and corrosion are the classic-car owner’s nemesis. Classic cars spend most of their existence in storage and only hit the road in the summer months. The rarity of these vehicles and their often treasured place in the hearts of their owners place extra importance on protection during extended periods of storage.

AMSOIL Z-ROD Synthetic Motor Oil is formulated with a unique blend of rust and corrosion inhibitors to ensure maximum protection during long-term storage. To prove its effectiveness, Amsoil submitted Z-ROD to the Standard Test Method for Rust Protection by Metal Preservatives in the Humidity Cabinet (ASTM D1748-10). This test evaluates the rust-preventative properties of oil under high-humidity conditions, similar to those faced by a covered hot rod in a damp garage. The metal coupon treated with Z-ROD showed no signs of rust.


Use AMSOIL Z-ROD Synthetic Motor Oil in engines requiring 10W-30, 10W-40 or 20W-50 motor oil. Z-ROD Synthetic Motor Oil meets API SL and earlier specifications, allowing for increased levels of anti-wear additives. ZDDP levels in Z-ROD Synthetic Motor Oil exceed the limits of API SM and newer specifications.

Service Life

Engines in classic cars, hot rods and other performance vehicles are modified, oil drain interval recommendation for these applications cannot be provided. Responsibility for determining the drain interval duration rests with the owner. As a general service guideline, the maximum drain interval for Z-ROD Synthetic Motor Oil should not exceed 5,000 miles

Why “Z-ROD”?

“Z” stands for zinc and “ROD” refers to the hot rods and other classics for which it’s designed. Lack of zinc in modern oils is a hot topic among classic-car owners, and many seek out high-zinc oils to protect their engines. Z-ROD is packed with zinc and phosphorus anti-wear additives to protect the classics