When shopping for engine oil to put into your car or truck, what do you look for? Sure, you might take into consideration the viscosity and the brand. But what about the additives? So many brands make promises that their engine oil works better because they have proprietary additives to work well. However, if you don’t know what an additive is or does, how can you make an informed choice? And even if you do know about additives, do you know what each one does or which ones are not worth your money?

To help you make the best choice for your vehicle, this guide will explain everything you need to know about engine oil additives. Let’s get started.

Everything You Need to Know About Engine Oil Additives header image

What is an Engine Oil Additive?

Typical engine oil is made up of base oil and additives. Around 10-30% of that formula belongs to additives. That may not seem like a huge amount, but it holds some real estate. So, what are they? An engine oil additive is a specialized chemical compound formulated to enhance the properties of engine oil in a vehicle. Manufacturers formulate engine oils with a combination of base oils and additives to meet specific performance standards and address various challenges faced by engines. These additives are carefully selected to enhance the overall functionality of the engine oil.

What Do Engine Oil Additives Do?

Performance additives, detergents, dispersants, viscosity index improvers, anti-wear agents, and antioxidants are some common types of additives found in engine oils. Each serves a specific purpose, such as improving fuel efficiency, preventing deposits and sludge, maintaining oil viscosity across temperature ranges, protecting against wear, and inhibiting oxidation.

Let’s take a more in-depth look at the various kinds of motor oil additives:

Performance Additives

Certain additives are added to motor oil to improve overall functionality, namely by influencing cold flow ability, viscosity stability, and protecting seals. If you live somewhere with a cold winter, then you are going to want to consider an engine oil that makes use of pour-point depressants.

A pour-point depressant helps lubricants flow faster in cooler weather by modifying the formation of wax. These ingredients include copolymer esters, alkylated naphthalene, polymethacrylates, and phenolic polyers.

Compounding with pour-point depressants are viscosity modifiers that help alter the viscosity of oil whenever temperatures increase or decrease. These viscosity modifiers ensure that your engine will be lubricated regardless of the temperature outside. The two most common viscosity modifiers are olefin polymers and copolymers, as they reduce the oil’s ability to thin out. You may also note the presence of dienes and alkylated styrenes or methacrylates.

One thing that also hinders performance is a leak. Oil is formulated with seal-swell agents like aromatic hydrocarbons and organic phosphates that keep the seal from becoming brittle.

Surface-Protection Additives

Automobile motor oils incorporate a variety of surface-protection additives to effectively address distinct challenges faced by engine components. These additives serve a crucial role in ensuring the longevity and optimal functioning of the engine by mitigating issues related to wear, corrosion, and deposits. Anti-wear agents, including phosphates, organic sulfur and chlorine compounds, sulfurized fats, sulfides, and disulfides, work to minimize friction and wear while preventing scoring or seizure through chemical processes that inhibit metal-to-metal contact.

Corrosion and rust inhibitors, such as zinc dithiophosphates (ZDDP), metal phenolates, fatty acids, and amines, play a vital role in preventing internal engine parts from succumbing to corrosion and preserving their structural integrity.

Detergents, encompassing metallo-organic compounds of sodium, calcium, and magnesium phenolates, phosphonates, and sulfanates, neutralize varnish and sludge, ensuring surfaces remain clean and deposit-free. Dispersants, including alkylsuccinimides, alkylsuccinic esters, and Mannich reaction products, contribute to keeping insoluble contaminants dispersed in the lubricant, preventing their agglomeration.

Additionally, friction modifiers, such as organic fatty acids and amides, high-molecular-weight organic phosphorus, and phosphoric acid esters, actively reduce friction, thereby enhancing fuel efficiency. The combination of these surface-protection additives in engine oil formulations plays a pivotal role in fortifying engine components.

Lubrication Enhancing Additives

Another form of protective additive is designed to enhance the oil’s lubricating properties. One of the ways lubrication-enhancing additives work is by counteracting foam. You do not want foam to build up in your engine. When churning engine parts start to mix air into the oil, foam builds. Within the air bubbles created, the moving metal parts can make contact with one another, getting damaged over time.

This is where anti-foamants, such as silicone polymers and organic copolymers, come in handy. Without these ingredients, there would be so much foam that it would spew from the dipstick whenever you went to do an oil change.

Another form of additive is an antioxidant. Again, you don’t want too much oxygen in your motor oil. The more air in the motor oil, the more it decomposes through oxidation. As such, antioxidants are used to eliminate peroxide and other free radicals happening within the oil to extend its life. Common antioxidants present in motor oil include aromatic amines, sulfurized phenols, hindered phenols, and zinc dithiophosphates.

Lastly, to slow down oxidation a bit further, metal deactivators are added to the formula. These compounds settle as an inactive layer throughout the engine to protect it. Metal deactivators like sulfides, amines, nitrogen compounds, and phosphites are common.

What Not to Do When It Comes to Additives

As you can imagine, engine oil additives are crucial when it comes to protecting your engine. Each brand looks at the available additives and considers how those ingredients are going to pair with their base oil formulations. Chemists must carefully think about how certain additives are going to interact, as well, to ensure that no unfortunate reactions happen within your engine. Any miscalculations with how an engine oil is formulated could result in more buildup, performance issues, and even engine damage.

For example, some additives fight for dominance in the engine, such as anti-wear and corrosion inhibitors. If there is too much of any of these additives, they will counteract the effectiveness of the other. In high-temperature regions, detergents will synergize with anti-wear additives, causing higher amounts of deposits to form. Furthermore, anti-foam additives cannot function optimally if there are too many dispersants and detergents in the same formula. Another thing to keep in mind is that adding too much anti-form additive will cause more foam, not less.

Knowing all this, here are two things you must not do when using additives:

  • Mixing Lubricants. Although conventional and synthetic oils are generally the same, you should never mix two different brands. Topping off your engine oil with a different brand will not do lasting damage, but you should not mix too many different brands, especially when changing your oil. The different additives in each formula could interact poorly, diminishing the effectiveness of your engine oil.
  • Using Aftermarket Formulas. Adding in aftermarket additives to your engine oil will only upset the delicate balance that exists, reducing the ability of the existing additives.

Can Additives Be Used to Supplement Low-quality Engine Oil?

Yes, additives can be added to cheaper engine oil after changing your oil. Should you do it that way? Not necessarily. Doing so is also not recommended. Engine oils are carefully formulated with specific additives during the manufacturing process to meet the requirements and specifications set by engine manufacturers.

Adding aftermarket additives to engine oil can sometimes cause more harm than good. Here are a few reasons why:

  • Compatibility Issues: Engine oils are designed with a specific additive package to provide the necessary lubrication, protection, and cleaning properties. Adding external additives might interfere with the existing formulation and lead to compatibility issues.
  • Unpredictable Reactions: Different additives may have unpredictable reactions when mixed. Some additives may not be compatible with the chemicals present in the original oil, leading to adverse effects on the engine.
  • Voiding Warranties: Some engine manufacturers may void warranties if aftermarket additives are used. This is because the use of additives can potentially lead to engine damage. Manufacturers want to ensure that their recommended oils and additives are used.
  • No Guaranteed Improvement: While some additives may claim to improve engine performance, fuel efficiency, or reduce wear, their effectiveness is often disputed. The benefits of using such additives may not outweigh the potential risks.

Instead of relying on additives to compensate for low-quality engine oil, it’s better to choose a high-quality oil that meets the specifications recommended by the vehicle manufacturer. Regular oil changes using the manufacturer-recommended oil grade and type are essential for maintaining the engine’s health and performance.

Final Thoughts on Engine Oil Additives

Understanding engine oil additives is crucial for making informed decisions about maintaining your vehicle’s engine. Additives play a vital role in enhancing oil performance, protecting engine components, and ensuring optimal functionality. From performance and surface-protection additives to lubrication enhancers, each type serves a specific purpose in maintaining the health of your engine.

Categories: Oil Guides


Hi, I’m Alastair. Welcome to SyntheticOil.me, a website for the best oil recommendations for your vehicle, whether it is a two-door sports car, SUV, hatchback, or tractor. Having grown up on a family farm and working as an engineer, I became interested in just about anything with an engine. I also found that motor oil, despite being essential for internal combustion engines, is overlooked, underestimated, or just misunderstood. There may come a day when motor oil is obsolete as electric vehicles become more and more popular. But until then, you are going to need to know the best type of motor oil for your vehicle. That is why I was inspired to create this website. SyntheticOil.me aims to be the internet’s destination for everything related to motor oil, including news, comparisons, features, and recommendations for vehicles by make and model. All the information you need to keep your treasured vehicles running clean is right here. In particular, I am also obsessed with the upkeep of vehicles in general. That is why you will also find troubleshooting tips for removing oil filters and drain plugs, for example. Consider it the mission of SyntheticOil.me to provide accurate information, as well as insight for automotive professionals and enthusiasts.


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