Whether its Mobil or Total, leading lubrication makers engineer solutions starting with the same formula.
Lubricants begin with a base oil that may be mineral, synthetic or semi-synthetic, and then specially selected additives are included. Additive packages can include inorganic or organic substances, and they improve the overall formula, giving it desirable characteristics. In this comprehensive guide, we’ll take a deep dive into lubricant additives and their role, and examine the different types that are included in a wide range of products – from grease to gear oil.
What is a lubricant additive?
Lubricant additives are inorganic or organic chemical compounds added to base lubricant stock to enhance its lifespan, performance and stability by supressing the base oil’s undesirable qualities, improving its existing properties or adding all-new functionalities.
How are lubricant additives made?
Additives are created via various chemical synthesis processes that produce specific inorganic or organic molecules that improve a lubricant’s performance. Selected additives are combined with a base oil in an oil-blending plant to make the finished lubricant product.
The primary role of lubricant additives
Typically, additives make up about 30 per cent of a lubricant product’s formula. Depending on their required purpose in the oil formula, lubricant additives perform different roles. For instance, additives like viscosity index improvers can improve the base oil’s existing properties, while an anti-foaming agent can reduce its unwanted characteristics. Anti-wear agents, on the other hand, give base oils all-new attributes.
Types of lubricant additives
There are multiple types of lubricants that break down into three categories. Depending on the role they play, additives may be surface protective, performance improving or fluid protective.
Surface protective additives (imparting new properties)
As the name indicates, surface protective additives are designed to protect metal surfaces of mechanical components.
Anti-wear agents
Formulated to reduce mechanical wear caused by friction, anti-wear (AW) additives effectively protect parts during metal-to-metal contact. The most common AW agent is ZDDP.
Extreme pressure additives
Designed for machines working in more demanding conditions that AW agents struggle to protect, extreme pressure (EP) additives react with metal surfaces and create a sacrificial protective film on metal surfaces. This stops the microscopic asperities on surfaces from seizing and welding during adhesive wear.
Detergents
Often alkali in nature, detergents also play a protective role. They can neutralise acids and keep heated metal parts clean. They are often added alongside dispersants.
Dispersants
These additives are designed to ensure unwanted debris is either suspended in oil for effective removal or dissipated. They work well with detergents, helping them neutralise more acid and ensuring unwanted particles stay suspended.
Corrosion and rust inhibitors
Designed to minimise or completely remove rust and corrosion, inhibitors form a protective barrier that defends metal surfaces against moisture and neutralises corrosive acids.
Performance enhancing additives
The main role of this group of additives is to improve the base oil’s existing properties.
Viscosity index improvers
Polymer additives, viscosity index improvers ((VIIs) prevent changes to lubricant viscosity during temperature increases. Sometimes referred to as viscosity modifiers, these additives boost fluid viscosity.
Pour point depressants
The term pour point refers to the lowest possible temperature where a lubricant remains fluid. When lubricants are subject to lower temperatures, wax crystals present in mineral oils can solidify, stopping an oil from flowing properly. Pour point depressants (PPDs) efficiently reduce the size of the crystals, allowing lubricants to flow even in sub-zero temperature operations.
Friction modifiers
Employed in automatic transmission fluids (ATFs) and engine oils, friction modifiers have an import role to play. Their main purpose is to alter frictional forces occurring between an engine and the components of the transmission.
Fluid protective additives
This additive class either reduces the impact of the base oil or minimises changes occurring over the service lifespan of the lubricant product, counteracting negative effects.
Anti-foaming agents (defoamants)
Sometimes called foam inhibitors, anti-foaming agents effectively reduce surface tension and stop bubbles forming in the lubricant. Indirectly, they may also reduce oxidation risk as they minimise contact between lubricants and air.
Antioxidants
Oxygen contamination degrades lubricant base oils. It encourages acid formation leading to corrosion, but also supports sludge build up. This increases viscosity, resulting in surface deposits.
Also known as oxidation inhibitors, antioxidants are among the most important additives and can be found in almost every lubricant formula. As protective additives, their job is to extend lubricating oil service life.
Metal deactivators
The main role of metal deactivators is to provide lubricant stability. They deactivate metal ions by forming a protective inactive film on metal surfaces.
When selecting a lubricant for a specific application, always consider its additive package to ensure it has the correct characteristics required.
