Advice From The Experts
To address the subject of reduced anti-wear additives in motor oil, we presented the same questions to representatives of AmsOil, Pure Power!, and Torco. We chose these companies because all are well known and have loyal followings, and because of their product lines. AmsOil is entirely synthetic, Pure Power! is all mineral based, and Torco offers both, so it seemed like a good opportunity to find out how each addresses this issue.
What is the purpose of zinc additives?AmsOil Zinc-based additives are used primarily as anti-wear agents to prevent premature wear of engine components. ZDDP is the most commonly utilized form, which also provides corrosion and oxidation protection.
Pure Power! Zinc is generally introduced to motor oil through its working partner, phosphorous; in tandem, they provide one hell of an anti-wear agent. It's, without question, the best we have, although there are some who claim XYZ polymer can perform the same task; however, it does not!
Torco Zinc dithiophosphate has been the chemistry of choice since the mid-'50s as the "anti-wear agent in high-performance oils." Zinc is better defined as an anti-weld agent because the surface asperities cannot connect or transfer in its presence. As the liquid oil transitions from a support separating fluid (hydrodynamic lubrication) to the touching or colliding asperity contact (boundary lubrication), the zinc instantly reacts and bonds, causing separation between the two moving surfaces. This is known as a chemical absorbed reaction layer, and the phosphorus counterpart to the zinc makes this possible. The phosphorus is the heat-seeking element that fluxes the zinc to the metal surfaces that are demanding protection from the metal-to-metal contact. The zinc dithiophosphate chemical is made from almost equal parts of zinc and phosphorus, or a 1:1 relationship.
Why were zinc levels lowered?
AmsOil Zinc levels were lowered in response to the American Petroleum Institute (API) SM and International Lubricants Standardization and Approval Committee (ILSAC) GF-4 oil specifications. The action was driven by original equipment manufacturers (OEM) based on the Environmental Protection Agency (EPA) mandate that emissions reduction systems needed to function for a specific period of time without failing. OEMs pushed to remove anything in motor oils that could potentially harm emissions reduction systems.
Pure Power! There are concerns that phosphorous/zinc may have a gradually crippling effect on catalytic converters, although there is no available data established that indicates how long it may take, nor how much oil consumption is involved to reach that point.
Torco Oil in the engine crankcase is constantly changing to vapors and is pulled by vacuum past the rings into the intake fuel air system. These vapors containing the element phosphorus contact the exhaust oxygen sensors and the catalytic converter. Because phosphorus is both heat-seeking and deposits residue at the same time, it changes the catalytic converter's ability to break down hydrocarbon fuel-type molecules, negatively affecting the oxygen sensors and catalytic converter operation.
What API designations have reduced zinc?AmsOil There has been a stepwise reduction in sulfur and phosphorus in API oil specification designations, which drove the reduction in ZDDP content. The current API SM gasoline motor oil specification limits phosphorus to a maximum of 0.085 percent. Sulfur is limited to a maximum of 0.50 percent for 0W-20/0W-30/5W-20/5W-30 and 0.70 percent for 10W-30 viscosity categories.
Pure Power! Pretty much all licensed motor oils are affected, with commercial grades being the least, but the internal engine component wear will increase regardless of the amount of reduction.
Torco In the years previous to 1997, zinc levels between 1,200 and 1,400 ppm could be found in all brands of high-performance motor oils. In 2001, API category SL was introduced with 1,000 ppm maximum phosphorus/zinc content; this was a mandatory 18 percent reduction. In 2005, the API SM category was introduced and "phosphorus/zinc" level was reduced again to a maximum 800 ppm (an additional 20 percent reduction, total 34 percent reduction from API SJ rating); this reduces the phosphorus/zinc to an inadequate level of protection for high-performance engines.
What problems does reduced zinc create?AmsOil Reduced zinc or ZDDP content has been linked to issues with premature wear in flat-tappet camshaft engines and, in particular, with engines that include high-tension valve springs or other modifications that create high contact pressures.
Pure Power! When the anti-wear agent is reduced, the rest of the additive pack receives a greater workload and engine wear will go up.
Torco When an engine transitions to WOT (wide-open throttle), elevated rpm, or when the applied load goes up, the oil film "goes down"; this situation can cause a potentially dangerous metal-to-metal contact issue. Increasing the oil viscosity grade will help with deeper, stronger films; today's engines (post 2001) are built to use lower-viscosity and lower-phosphorus/zinc-rated oils. The way in which these new engines are built and the lower demands on components such as valvetrains and cams is such that the requirement for zinc protection is not the same as in previous years. Engines produced before 2001 are put in jeopardy from reduced phosphorus/zinc content.
Are there other additives that provide the same protection as zinc?AmsOil AmsOil markets and sells motor oils that contain additive packages that replace a portion of the ZDDP component. AmsOil also offers the Premium Protection line of motor oils that have higher levels of ZDDP.
Pure Power! Not really, especially where cam/lifters pushrod tips and wrist pins are concerned.
Torco Torco USA started using another metal supplement to zinc in 1972; it was found that engine wear would be greatly reduced if organic liquid molybdenum was added to zinc and phosphorus. Through the years, Torco has adjusted the combination of zinc, phosphorus, and liquid moly, but Torco MPZ is the secret formula/ingredient for all Torco products.
Do you recommend specific break-in additives for high-performance engines?AmsOil AmsOil does not currently provide any break-in additives. The use of an additive during the break-in period (as opposed to an ongoing treatment) is only advisable in conjunction with a high-quality lubricant for flat-tappet cams. The break-in period is when flat-tappet camshafts are most vulnerable to failure. We also recommend that street rodders use a high-quality assembly lubricant. (Talk to the manufacturer of your camshaft engine.)
Pure Power! Not really, especially where cam/lifters pushrod tips and wrist pins are concerned. I have built and raced cars for 45 years-everything from Super Stocks to Fuel Altereds-and it is my experience that a good commercial-grade 10W/30 or 15W/40 motor oil will handle the break-in/seating chore quite satisfactorily.
Torco Engine break-in and good standards and procedures are critical to the life of a high-performance engine. This process should include assembly lube products for bearings and bottom-end in liquid form; a "gel" version of the assembly lube should be used for cam lobes and pump drives. A mineral-based break-in oil will add protection and allow for piston rings to seat. This is a critical step when planning to switch to synthetic oil after break-in. We offer a break-in additive with high levels of anti-wear and anti-friction MPZ for added protection.
Do you recommend any oil additives for normal operation?
AmsOil AmsOil does not recommend using any oil additives, since there is no need to consider use of any oil if the motor oil is formulated correctly for the application. Oil additives focused on extreme pressure or anti-wear resistance may appear to initially help with these particular properties but upset the balance in other areas and can promote acidic corrosion, excessive oxidation, and foam, for example.
Pure Power! This is an area where so many people are led astray. There are companies that tout their oil additive as being fundamentally urgent for all cars, trucks, motorcycles, airplanes, boats, etc. I would not recommend any oil additive for any reason, especially the thick/liquid plastic variety that claim to afford so much engine protection by adding one or two bottles to the engine oil. Those are especially deadly because they will actually interfere with ring sealing as well as being acidic.
Torco For the high-performance, racing, and hot rod market, we recommend adding a zinc-enhanced additive such as Torco ZEP. This additive alone has the appropriate amount of zinc and phosphorus, along with molybdenum for additional protection to bring up to six quarts of API SM motor oil to 1,200-ppm zinc/phosphorus content.
Many engine builders recommend the use of diesel oil in vintage/flat-tappet engines. Is that a viable option?
AmsOil The assumption is that diesel oils contain high levels of ZDDP, which cannot be found in other motor oils. This recommendation is partially correct. First, make sure the diesel oil carries gasoline credentials; some do not. If the diesel oil is recommended for gasoline use and it contains a healthy dose of ZDDP, it may be a viable option. Be very careful not to generalize that all diesel oils contain high levels of ZDDP; this is not the case. Modern API CJ-4 type oils have lower levels of ZDDP than their predecessors.
Pure Power! Any commercial-grade motor is more than acceptable, either in 10W/30 or 15W/40. Over the road, tractors pulling two or three times their weight go as far as two million miles using diesel/commercial-grade motor oil, so it can handle anything you throw at it-including nitro-burning Top Fuel cars.
Torco Diesel engine oils do contain higher levels of zinc than API SL and SM automobile oils, while diesel oil provides essential zinc/phosphorus levels. Unfortunately, diesel oils also add significant levels of detergents and potential "non-compatible" elements to the mix. Diesel engine oils have to be made to deal with heavy sculpture fuels and engines in a wide variety of climatic conditions. Race oil formulations can be adjusted to best suit extreme temperature and loads not necessarily addressed in a diesel engine application. Using race oil will provide an acceptable level of zinc/phosphorus to provide acceptable anti-wear protection.
Are racing oils subject to lowered zinc levels?
AmsOil The low phosphorus levels as required by API SM apply only to 0W-20 through 10W-30 viscosity ranges. Racing oils are typically higher viscosity and anything above a 30 weight is not required to have low levels of phosphorus, even if it is API SM. Most racing oils are expected to contain high levels of anti-wear protection since durability is their main purpose. AmsOil racing oils contain high levels of ZDDP.
Pure Power! In the past 20 odd years, we have had occasions to have ICP analysis performed on three "racing" motor oils. The additive package that was being employed in those oils was really pretty weak. In fact, one of the oils actually had more working ingredients in the regular motor oil version than in the "race formula" motor oil.
Torco A product listed as race oil is exempt from the API ratings issue; these products are not recommended for vehicles with catalytic converters. Torco SR-5, TR-1, and SR-1 race oils are exempt from API ratings and all contain levels in excess of 1,200 ppm zinc/phosphorus.
Are racing oils a good option for street-driven performance engines?AmsOil That is dependent on the brand and formulation. Racing oils designed exclusively for the track many times do not contain appropriate levels of detergents and dispersants required for longer-term street use. These formulations would not provide adequate protection against engine sludge, rust, oxidation, and attack from acids and other combustion byproducts. The best advice is to talk with a reputable manufacturer, ask informed questions, and make decisions based on the actual specifications.
Pure Power! Based on my experience, I would not recommend an off-the-shelf race oil. I would much prefer a commercial/diesel motor oil.
Torco As discussed in the previous questions, the issue is engines pre-/post-2001; if there is no catalytic converter, then "race oil" can be used, which means increased levels of zinc/phosphorus.
Do higher viscosities provide any better protection in oils with lowered zinc levels?
AmsOil Higher-viscosity oils may help somewhat with extra protection, but a strong anti-wear package is required to protect your investment with regards to flat-tappet camshaft engine applications, especially with modifications, including high tension valve springs.
Pure Power! No, they do, however, lead to more cylinder blow-by/cylinder leakage, not to mention greater fuel consumption.
Torco Higher-viscosity oils provide deeper/stronger films with more hydrodynamic contribution than lower-viscosity oils. If an engine is a large displacement, like what is found during the musclecar era, a SAE 20w50 is usually recommended.
Which of your oils would you recommend for flat-tappet engines, particularly older high-performance engines with higher-than-stock valve spring pressures?
AmsOil The AmsOil Premium Protection 10W-40 (AMO) and 20W-50 (ARO), and racing oil 20W-50 (TRO) are higher-viscosity oils that contain high levels of phosphorus and zinc anti-wear additives. AmsOil diesel oils, 5W-30 (HDD) and 10W-30 (ACD, are lower-viscosity products qualified for gasoline engines that also contain high levels of ZDDP anti-wear additives.
Pure Power! Our 10W/30 CH-4/SJ or 15W/40 CI-4/SL high TBN reserve can quite easily handle seat pressures in excess of 225 lbs.
Torco All Torco race oils-both mineral and synthetic; TR-1, SR-1, and SR-5-are designed for the most severe race and high-performance engines.