The debate on oil additives continues and is hotly debated by enthusiasts that are convinced that aftermarket oil additives work and those that are convinced that they do not work and may even be detrimental to engine lubrication. Both sides of the argument have taken a firm stand and drawn lines in the dirt.

A couple of court cases aimed to protecting consumers from marketers in the early 90’s helped to attach a stigma to oil additives. Even today that reputation still exists to some degree. It’s almost as if aftermarket oil additives are guilty until proven innocent.

We wanted to know the factual details on engine oil additives and help clear up the mystery and assumptions associated with additive packages. If you hang in there with us, we’ll present the black and white facts and let you come to your own conclusions.

Certified motor oils contain the necessary additive packages.                     – George Elliott

The Experts

We chose representatives from some of the most highly respected companies that have a dog in this fight. Getting insight from these experts, combined with the letter of the law, we should be able to prove if engine oil additives help, do nothing or hurt engine performance. Our expert panel:

Representatives from zMAX and Royal Purple Synthetic Oil served as our experts in this article

Hot Button

Oil and oil additives are one of those “hot button” topics that can start major flame wars on internet forums. Our objective is to stay away from the guessing and tackle the facts, so let’s start with this: nearly all commercial motor oils, synthetic and petroleum based, contain additives. That is a fact.

Only the American Petroleum Institute (API) SA rated motor oils have no additives. Interestingly enough, the API SA rating has been made obsolete by the agency with a statement declaring “Caution: Contains no additives. Not suitable for use in gasoline-powered automobiel engines built after 1930. Use in more modern engines may cause unsatisfactory performance or equipment harm.”

Without additives, motor oil would have a tendency to breakdown sooner and be unable to protect engine parts at higher temperature ranges. Other additives provide contaminant control, seal conditioning and corrosion inhibiting properties.

According to zMAX’s George Elliot, “Certified motor oils contain the necessary additive packages.” Royal Purple’s Chris Barker advises, “Do your research. Each motor oil has a different quantity of additives. It’s like shoes. Each has a specific application or purpose. You have running shoes, walking shoes, dress shoes, dancing shoes… you need to pick the right shoe for the purpose. Dress shoes for running probably won’t perform as well.”

From out of the ground to a refinery, how much help does Mother Nature really need?

Types of Additives

According to Ullmann’s Encyclopeida of Industrial Chemistry (ISBN: 9783527306732), additives to motor oil can comprise up to 5% by weight of the oil. The additive package and choices of additives depend on the intended application and usage of the oil. It’s not a marketing ploy to label some bottles of motor oil as diesel motor oil and others as outboard motor oil. The demands of the engine lubrication are different between these radically different engines, therefore the additives in the motor oil are different to meet these needs.

“Motor oil companies manufacture their products to meet auto maker standards. Because of that, the auto makers will advise you not to add any aftermarket additives,” said Elliott. Barker also stated, “as soon as you pour an additive into your engine, you have taken it into your own hands to become a chemist. Most of the aftermarket oil additives are inert enough not to cause any problems, but in some cases it’s not good.” A little research can go a long way.

From what our experts explained to us, it’s not correct to believe that all oil additives used in packaged engine oil are bad and all aftermarket oil additives are great. It’s a matter of understanding the demands of your engine and the purpose of the motor oil and chemicals you put into it. Lets take a look at the different additives that are blended in to motor oils or offered as after market oil additives:

Additives for Controlling Chemical Breakdown

  • Detergent additives are used to clean and neutralize oil impurities which would normally cause deposits (oil sludge) on vital engine parts.
  • Corrosion or rust inhibiting additives retard the oxidation of metal inside an engine.
  • Antioxidant additives retard the degradation of the stock oil by oxidation.
  • Metal deactivators create a film on metal surfaces to prevent the metal from causing the oil to be oxidized.

Example of the viscosity of milk and water. Liquids with higher viscosities make smaller splashes when poured at the same velocity. Photo by Henningklevjer

Additives for Viscosity

  • Viscosity modifiers make an oil’s viscosity higher at elevated temperatures. This combats the tendency of oil thinning out at higher temperature. Most multi-grade oils have viscosity modifiers. Some synthetic oils are engineered to meet multi-grade specifications without them.
  • Pour point depressants improve the oil’s ability to flow at lower temperatures.

For Lubricity

  • Friction modifiers or friction reducers are used for increasing fuel economy by reducing friction between moving parts. Friction modifiers alter the lubricity of the base oil.
  • Extreme pressure agents bond to metal surfaces, keeping them from touching even at high pressure.
  • Antiwear additives or wear inhibiting additives cause a film to surround metal parts, helping to keep them separated.

For Contaminant Control

  • Dispersants keep contaminants suspended in the oil to prevent them from coagulating.
  • Anti-foam agents inhibit the production of air bubbles and foam in the oil which can cause a loss of lubrication, pitting, and corrosion where entrained air and combustion gases contact metal surfaces.
  • Antimisting agents prevent the atomization of the oil.

In addition to the specialized oil additives mentioned above, some other additives are blended into the motor oil for other purposes like seal conditioners. Seal conditioners cause gaskets and seals to swell so that the oil cannot leak by. Elliott cautions against expecting too much from some aftermarket oil additives that promise to stop leaks or stop oil burning problems. “If there is mechanical damage causing excessive oil loss or burning, like damaged valve seats or a broken piston ring, no oil or additive is going to fix that. The mechanical damage has to be fixed in order to stop the problem,” he states.

Barker cautions, “Consumers should be aware if a company only tells you one thing about their product. It could be a masking additive that hides one problem but creates others. Consumers looking to increase their oil pressure, because they have heard that is what you need, may add a thickener that raises oil pressure but what they really needed was oil flow.”

Molybdenite is the principal ore from which molybdenum metal is extracted. In its appearance and feel, molybdenum disulfide is similar to graphite and is frequently used as a friction reducer.

What To Look For

Elliott explained that additives that have a lot of detergents or other chemicals, “that can change the lubrication properties of motor oil. Many consumers pay good money for top quality oil and the last thing you want to do is change the protection level of the oil.”

All of the current API motor oil in gasoline catagories have placed limitations on the phosphorus content for certain SAE grades. Phosphorus has been used for it’s anti-wear properties in motor oils. The most common anti-wear additive is Zinc dithiophosphate. As the API introduces new grades, the successively lower limits on phosphorus and zinc limits have caused problems in engines with flat tappets.

Barker explained that the flat tappet cam failures were caused by a number of issues not just a reduction in phosphorus in motor oils. “The initial flat tappet cam failure problems coincided with offshore manufacturing of cams and the materials used in the construction of these camshafts and enthusiasts using increased valve spring pressures. Combined with the reduction of Zinc dithiophosphate in motor oil, this was the perfect storm to cause the problem. Any one of these things individually would not have been a problem, but the combination of them was a recipe for the failures that we saw.”

API's Engine Oil Licensing and Certification System (EOLCS) is a voluntary licensing and certification program that authorizes engine oil marketers who meet specified requirements to use the API Engine Oil Quality Marks—the API Service Symbol "Donut" and Certification Mark "Starburst." This program is a cooperative effort between the oil industry and vehicle and engine manufacturers Ford, General Motors, and Chrysler; the Japan Automobile Manufacturers Association; and the Engine Manufacturers Association.

The API represents most of the world’s automobile and engine manufacturers and their standards for normal street usage. There are special cases however, like high performance engine or fully race built engines where the protection requirements are above and beyond the API requirements. These groups, working within governmental regulations, are concerned with meeting the increasingly stringent emission laws than meeting the ultimate lubrication properties that an engine wants.

To meet these special situations, engine oil manufacturers offer speciality oils that contain higher than API allowed phosphorus levels. The reduction of phosphorus and other anti-wear chemicals in motor oil has been identified as causing failures of camshafts and other high pressure bearings in older engines with flat tappets or engines with older engine architecture.

Elliott explained that consumers need to avoid the common trap of “if a little is good, then a lot is better” mentality. “Don’t mix multiple brands of additives,” he advises, adding “follow the usage instructions on the package.”

Consumers that want to top up their oil level or change the engine oil should pay close attention to the oil label for ratings and markings that indicate what the motor oil blend was designed for. The blend is different for gasoline engines and diesel engines. Sometimes the oil manufacturers have specific oil blends for naturally aspirated engines and forced induction engines. In order for motor oil to work as designed, the user must follow the directions given by the oil maker and used the intended equipment.

An example of how having the same size pasta in the bowl helps with traction. Photo from Gordon Wright Blogspot

Synthetic or Mineral Oils and Additives.

Before we let you go on your merry way thinking that synthetic oils are always made in a petri dish is some laboratory, let us be the ones to tell you that they are not. Synthetic lubricants are manufactured using chemically modified petroleum components rather than whole crude oil. The difference being how the crude is processed. According to Barker, synthetics are highly refined and the molecules are realigned in the process. “Synthetic oil, from an engineering standpoint, is not building the oil molecule by molecule. It’s like taking a big bowl of pasta with all the different types of pasta and separating the different types until all you have left is elbow marcaroni,” he said, adding “in addition to having a uniform molecule size, impurities likes waxes and sulfer are removed when formulating a synthetic oil. All of this results in lower traction properties and reduced friction.”

What Does All This Mean To You?

For the average consumer, it’s important to know what the additive packages or aftermarket additives are designed to do. Barker points out that, “race oil is manufactured for high performance engines that are rebuilt much more frequently than engines that are solely used on the street for thousands of miles. The additive package in race oil is most likely there to modify the oil’s viscosity without as much concern for contaminant control because of the lower milage before engine rebuilds. Motor oils manufactured for street use take into consideration the higher usage range and probably engineered with more contaminant and chemical breakdown control.” Using the product designed for your application is probably going to result in the outcome you desired when it was added to the engine.

Elliot agrees that consumers need to use the products that are designed for your application and, “understanding what, if any, changes occur to the motor oil when aftermarket products are used. It’s important to realize that our zMAX Micro Lubricant does not change the API rating of the formulated motor oil.” According to Elliot, “zMAX works with oil to make lubrication better.” Which guides us to the ultimate point when using aftermarket oil additives; know exactly what changes are made to the engine oil before adding anything extra because you may be changing the performance of your base oil.

Regardless of the type of motor oil, synthetic, conventional of a blend of both, the high level of engineering in engines and aftermarket automotive parts dictates that additives are even more important than ever. Warranty compliance, API licensing and level of protection for each application are critical keys for the oil manufacturers moving forward in the industry. Taking what we’ve learned from our experts, the only way to be truly prepared is to be knowledgeable consumers and do our homework. To paraphrase Royal Purple’s Chris Barker; make sure that you buy running shoes if you are going running.