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Engine oils, greases and lubricants have come a long way from the viscous mineral oils of yesteryear. Today’s equipment and vehicles are lubricated with highly formulated oils featuring synthetic chemical compounds and oil additives to push their capabilities even further. But what are oil additives and how do they work to protect components and enhance performance?

What are oil additives?

Oil additives are chemical compounds that improve the capabilities of lubricants, improving base oil characteristics, neutralising negative properties and adding new qualities. Lubricant additives can make up to 30% of an engine oil, but are used in very specific volumes – too much additive can often reduce the overall effect of the oil.

To ensure the quality, performance and lifespan of motor oils, additives are added to both mineral oils and synthetic oils.

Type of additive Role of additive

Oxidation inhibitor additives

Over time, motor oil oxidises. It lubricates engine parts less effectively. That’s why motor oil must be changed regularly. However, the oxidation inhibitor additive slows this process, improving the motor oil’s lifespan.
Detergent additives The main property of a detergent additive is to remove the deposits and microparticles that form on surfaces when the vehicle is used.
Dispersant additives Dispersant additives keep all the deposits and impurities that form when the engine is running in suspension, thus avoiding deposit build up on engine parts. The deposits are then carried to the oil filter.
Antifoam additives The use of detergent additives can generate foam on the surface of the oil. This prevents the oil from lubricating engine parts properly. This additive is used to prevent this occurrence.
Anti-wear additives Also called friction modifier additives, anti-wear additives add a layer of solid oil that lubricates the engine as soon as the vehicle starts up, thus avoiding friction between parts. This additive is mostly used in mineral oils.
Corrosion inhibitor additives An engine is made of metal parts that are sensitive to rust. Corrosion inhibitor additives protect parts from rust.
Viscosity index modifiers These additives reduce the difference in viscosity between cold oil and hot oil.
Antifreeze additives These additives help adapt the various motor oils to their environment by modifying the oil’s hardening temperature. They increase the fluidity of cold oil.


This list contains the main additives, but is not exhaustive. There are other types of additives as well.

How do oil additives work? 

There are many different engine oil additives available, working in a range of ways:

  • Anti-oxidants – These stop oxygen from reacting with component materials, reducing corrosion and sludge formation.
  • Anti-wear agents – Anti-wear agents attach to metal surfaces and stop metal parts from wearing against one another. Usually dormant, they react when metal surfaces touch, forming a soapy film that reduces friction.
  • Extreme pressure additives – Similar to anti-wear agents, extreme pressure additives react with component metals to create a film that stops adhesive wear. Activated by high loads and contact temperatures, they are a common fixture of gear oils.
  • Viscosity index modifiers – These stop oil from thinning out at higher engine temperatures. Made from polymers, they become larger as they heat up and thicken oil, before shrinking in size as conditions cool down, ensuring viscosity at a wide temperature range.
  • Anti-foaming agents – These chemicals have low interfacial tension, meaning they can enter the walls of bubbles, dilute and split them. As well as tackling foaming, they can also reduce oxidation as they remove the presence of air.
  • Detergents – Detergents clean the engine of deposits and sludge, as well as counteracting any acids that form within the engine and oil. They are the foundation of the oil’s alkalinity, noted by the oil’s base number.
  • Friction modifiers – Chemicals that lower the friction between engine components, Friction modifiers are typically used in transmission systems and help improve fuel economy, increase component lifetimes and reduce deposit formation.
  • Pour point depressants – An oil’s pour point refers to the lowest temperature at which it stays fluid. Pour point depressants allow oils to flow at lower temperatures, reducing the ability of wax crystals to form large, solid structures.
  • Dispersants – Dispersants stop soot particles from forming large deposits within engine oils. Comprising a polar particle that seeks out soot and an oil-soluble tail, they blanket pieces of soot and stop them from sticking together or to components, spacing them out within the oil, until the deposits are removed during the next oil change.
  • Emulsifiers – Used in fluids combining water and oil such as metalworking fluids, emulsifiers are chemicals that stop oils and water from separating by binding the two together.
  • Demulsifiers – Demulsifiers change the interfacial tension of lubricants to stop the formation of water-oil solutions. They are used in applications where there is a large amount of water or steam present during operations.
  • Tackifiers – Tackifiers stop lubricants from being propelled off components as they move – particularly rotational movement. They are usually used in the most viscous oils
  • Biocides – Biocides stop bacteria from growing within lubricants, keeping them clean from contamination and safeguarding their performance.

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