The need for a motor oil with high zinc content is especially important for classic and high performance vehicles such as hot rods, muscle cars, etc. Engines in classic and high performance vehicles typically run flat-tappet camshafts. The lifters and cam lobes on flat-tappet camshafts slide quickly against each other. This rapid sliding action creates a tremendous amount of friction and heat. Over time, this friction and heat between these two components will over time start to wear the cam and disrupt efficient valve operation. The end result is a loss of engine power and a reduction in efficiency.
Also, the specific areas of the flat-tappet camshafts, cam lobes, and lifters are splash lubricated instead of pressure lubricated, such as in other areas of the engine. This splash lubrication adds more strain on the anti-wear additive chemistry, which is made up of zinc and phosphorous, also known as zinc dialkldithiophosphate (ZDDP).
Typical motor oils available on the market simply do not contain sufficient amounts of ZDDP to adequately protect and perform in classic and high performance vehicles whose engines utilize flat-tappet camshafts.
One manufacturer that engineers a motor oil with high zinc content is AMSOIL. AMSOIL Z-ROD® Synthetic Motor Oil is a custom engineered oil specifically for classic and high performance vehicles. Its unique formulation contains high amounts of zinc. This robust volume of zinc helps to protect and prevent wear on flat-tappet camshafts. Additionally, AMSOIL Z-ROD® Synthetic Motor Oil is also blended with the finest thermally stable synthetic base stock oils. Added to this high zinc formulation is an exclusive and proprietary chemistry that contains the finest and heaviest duty corrosion and rust inhibitors.
The addition of this unique rust and corrosion chemistry gives this motor oil the added protection needed when your classic or high performance vehicle is being stored for a long period of time. Z-ROD® Synthetic Motor Oil is engineered to provide superior performance and protection when your vehicle is cruising down the road or in long term storage.
Maximum Protection for Engine Components
With its high volume of zinc and phosphorous, AMSOIL Z-ROD® Motor Oil will offer maximum protection for flat-tappet cams, lifters, cam lobes, rockers, and other components that are susceptible to friction and wear. This motor oil contains a generous volume of zinc and phosphorous that gives your classic car engine the highest level of protection against wear for those components that are splash lubricated.
Many valuable high performance vehicles and classic cars from a bygone era are fully restored to new condition. They are most likely stored over long periods of time and only when weather is sunny and dry are they taken out to be enjoyed. In many cases, these hot rods and classic vehicles are covered and stored in a damp garage. To protect critical internal engine components from moisture, corrosion, and rust, it is important that the motor oil offer the required protection from moisture and any rust or corrosion that could develop.
AMSOIL Z-ROD® Synthetic Motor Oil was specifically designed with its own proprietary blend of rust and corrosion inhibitors. To prove its ability to provide superior protection during long term storage, Z-ROD® Synthetic Motor Oil was put through the ASTM D-1748 standard test method for rust protection in the humidity cabinet.
The object of this test is to analyze a lubricant’s rust preventative properties under extreme high humidity conditions. These types of high humidity conditions would be in direct comparison to the high humidity conditions faced by a covered or stored hot rod or classic car in a storage facility. The test was conducted between a competitive oil versus AMSOIL Z-ROD® Synthetic Motor Oil. Two metal strips were treated, one with Z-ROD® Synthetic Motor Oil, the other with a competitor’s motor oil.
After 192 hours, AMSOIL Z-ROD® Synthetic Motor Oil showed no signs of corrosion or rust on the metal strip that was placed in the humidity cabinet. In comparison, the competitor’s motor oil failed the test after 24 hours. In fact, after the full 192 hours in the humidity cabinet, the metal strip treated with competitor’s motor oil showed severe rusting.
Superior Base Oils for Classic Cars
When protecting your classic or high performance vehicle’s engine, not only is it important that it be formulated with a high percentage of zinc and phosphorous, but also the choice of base stock oils used in the formulation. A lubricant manufacturer has two choices when formulating an engine oil. The chemist can use a lower cost petroleum base stock oil. A mineral base oil is pulled from the ground and refined to the point where it can be a useful oil for motor oil. Unfortunately, mineral or petroleum base oils come with unwanted byproducts. These byproducts can eventually lead to deposits, sludge, and varnish inside your precious hot rod engine.
Additionally, there are other natural shortcomings to a mineral based oil. The molecular makeup of a mineral or petroleum base stock oil consists of different sized molecules. These different sized molecules flow with some fluid friction. This fluid friction comes with unwanted friction in your engine. Over time, this fluid friction generates excessive heat, which can lead to thermal breakdown.
Another byproduct to a mineral base stock oil is the wax content naturally found. This wax content can cause the oil to thicken during cold weather and cold dry starts. Note that 80% of all engine wear occurs during cold dry starts. When your classic hot rod is pulled out of storage and the engine is turned over and started, unfortunately 80% of your wear is occurring during this time if your engine is being lubricated with mineral based oil.
The other choice that a lubricant chemist can make when designing a motor oil for classic hot rods or high performance vehicles would be a synthetic base stock oil. Synthetic base oils are man made. Their molecular structure contains perfectly and evenly sized molecules. Unlike mineral base oils, synthetic base oils have no unwanted byproducts.
Due to synthetic base oils have an even sized molecular structure, they flow without fluid friction. Having a base oil that does not create fluid friction helps in dramatically reducing wear in an engine. If your vehicle was running a mineral base oil and then a switch was made to pure synthetic motor oil, you would notice lower operating temperatures, better fuel economy, and more engine power due to the reduction of fluid friction provided by synthetic base stock oils.
Your classic hot rod engine benefits in many ways when protected with a motor oil formulated with pure synthetic base oils. These synthetic base oils are highly thermally stable. They withstand tremendous amounts of heat. They have a naturally high viscosity index. Having a high viscosity index means the oil will maintain the required viscosity over a broad range of temperatures. It will be unaffected by cold weather and hot temperatures.
Because the oil is man made and contains no unwanted byproducts, your engine will stay clean and free of deposits, sludge, and varnish. Additionally, AMSOIL Z-ROD® Synthetic Motor Oil is available in two viscosities: 10W30 and 20W50. To make sure both multi-viscosity oils stay in-grade, AMSOIL uses only the absolute finest heavy duty shear stable viscosity improvers. Shear stability is another way to analyze whether one oil is superior to another oil.
Shear stability in a motor oil can best be explained by a coiled spring. When an oil has not reached full operating temperature or the temperature is cold, the coiled spring is compressed. When the coiled spring is compressed, this simulates the lower number of the multi-grade engine oil. For example, 10W or 20W means that the coiled spring will only compress enough so the oil stays within those winter ranges. As the engine heats up, this coiled spring expands. This expansion causes the oil to thicken. These specialized coiled springs or VI improvers allow the oil to thicken to either a 30 weight or 50 weight motor oil.
When you apply gas to your engine and the engine starts to rev at the higher RPMs, your motor creates a tremendous amount of shearing action. Imagine this shearing action is literally a high revving scissors or shear that is trying to cut the springs of the coil. Regular or conventional type motor oils unfortunately utilize viscosity improvers that are low shear, meaning they are cheap coiled springs that are not able to withstand high shearing action.
What happens when a VI improver (coiled spring) shears down? As the coiled spring shears, your 30 weight oil shears down to 20 weight. Once this shearing has happened, it will not go back to a 30 weight oil. This constant shearing of the viscosity improver will continue until the oil no longer can even reach SAE 15 or 10. AMSOIL Z-ROD® Synthetic Motor Oils utilize extremely stable VI improvers. These VI improvers stay in-grade even when exposed to tremendous amounts of shearing.
Z-ROD® 20W30 will remain a 10W30 over the recommended drain interval. The same type of protection can be realized with the 20W50 Z-ROD®. There is only minimal shearing degradation towards the end of the oil’s service life.
By switching to a motor oil with high zinc content with robust volumes of rust and corrosion inhibitors, the foundation of the oil made with synthetic base stock oils along with shear stable viscosity improvers, your classic hot rod, muscle car, or high performance vehicle will have the kind of protection it needs to maintain maximum power and long term service life.
If you have an older or modified engine that calls for a 10W30 or 20W50 motor oil, then AMSOIL Z-ROD® Synthetic Motor Oil would be the correct choice. Z-ROD® is formulated to meet API SL and earlier specs. These specs do allow for increased volumes of anti-wear additives, such as those found in Z-ROD® Synthetic Motor Oil. The zinc levels found in Z-ROD® motor oil exceed the limits of API SN and newer specifications.
When the question arises whether an oil such as AMSOIL Z-ROD® Synthetic Motor Oil is compatible with regular or other synthetic motor oils, the answer is yes. Z-ROD® can be mixed with other oils, but it is important to understand that by mixing with other oils, performance benefits will be reduced, along with the oil life expectancy will be shortened.
It is not recommended to add aftermarket oil additives to AMSOIL Z-ROD® Synthetic Motor Oils. Its chemistry contains everything required at the maximum levels and is finely balanced and engineered to provide the best in performance and protection. Adding aftermarket oil additives will only disrupt this finely engineered chemistry.
Motors in hot rods, classic cars, and other high performance vehicles are typically modified. To provider a standard or universal oil drain interval recommendation is not possible. When running AMSOIL Z-ROD® Synthetic Motor Oil, it is the responsibility of the owner of the vehicle to decide when is the best time to drain the oil. The most scientific way to determine oil drain intervals is to take a sample of the oil and get it analyzed at an engine oil analysis laboratory.
With that said, there is a general guideline to follow in regards to Z-ROD® synthetic motor oil. Z-ROD® has a maximum drain interval of 5,000 miles or 1 year of service, whichever comes first. For highly modified engines that run nitrous or forced induction, then the absolute maximum drain interval must not exceed 3,000 miles or 1 year, whichever comes first.
In summary, run only a motor oil with high zinc content that is engineered with synthetic base stock oils. Your classic car will thank you and provide you with many years of enjoyable service.