The Significance of the Role of Viscosity Index Improvers

The Significance Of The Role Of Viscosity Index Improvers

Viscosity index improvers (VIIs), also called viscosity modifiers, are fascinating additives used in lubricants to maintain a stable viscosity across a wide temperature range. Here’s a breakdown of what they are and how they work:

What is a Viscosity Index Improver?

Think of VIIs as tiny polymer chains that act like temperature-sensitive sponges in the lubricant. At low temperatures, these chains stay coiled up, allowing the lubricant to flow easily for quick engine startup. As the temperature rises, the chains unfold and expand, creating a thicker film in the lubricant. This increased viscosity ensures proper lubrication and protection for engine parts even in hot operating conditions.

Why are VIIs important?

VIIs are crucial for multigrade oils, like your car’s 5W-30 oil. Without them, the oil would be too thick at cold temperatures, hindering startup and potentially damaging the engine. Conversely, it would be too thin at high temperatures, failing to provide adequate protection and leading to increased wear and tear.

Benefits of using VIIs:

  • Reduced friction and wear: By maintaining a proper viscosity, VIIs minimize friction between moving parts, leading to less wear and tear and extending the engine’s lifespan.
  • Improved fuel efficiency: Thicker oil at high temperatures reduces internal engine friction, which translates into better fuel economy.
  • Enhanced cold-start performance: VIIs ensure the oil flows easily at low temperatures, allowing for quick engine lubrication during cold starts.
  • Wider operating temperature range: Multigrade oils enabled by VIIs can function effectively across a broader temperature spectrum, reducing the need for seasonal oil changes.

Applications of VIIs:

VIIs are not just for engine oils. They are also used in various lubricants, including:

  • Transmission fluids
  • Gear oils
  • Power steering fluids
  • Hydraulic fluids
  • Greases

Limitations of VIIs:

While VIIs offer immense benefits, they have some limitations:

  • Shear degradation: High shearing forces can break down the polymer chains, reducing their effectiveness over time.
  • Cost: VIIs can be expensive to formulate, potentially increasing the cost of lubricants.

Overall, VIIs are innovative additives that play a crucial role in modern lubrication technology. They contribute to engine longevity, fuel efficiency, and consistent performance across diverse operating conditions.

In this blog, we will delve into the realm of viscosity improvers, exploring their significance, functions, and impact on engine performance.

What Is Viscosity Index Of Lubricant?

The viscosity index of a lubricant is a numerical measure indicating the extent to which its viscosity changes with temperature. Higher viscosity index values suggest minimal viscosity change over a temperature range, indicating better viscosity-temperature performance for the oil.

Viscosity Index Classification

The Viscosity Index (VI) classification by the Society of Automotive Engineers (SAE):

Above 110Very high
80 – 110     High
35 – 80       Medium
Under 35   Low

Viscosity Index Improver Formula

Viscosity Index Improver Formula

The formula for determining the viscosity index (VI) of an oil involves the kinematic viscosity values at 104 °F (40 °C)and 100 °C (212 °F), denoted as U and Y, respectively.

Additionally, it incorporates the viscosities at 40 °C for two hypothetical oils with VIs of 0 and 100, represented as L and H. These hypothetical oils share the same viscosity at 100 °C as the oil under investigation.

The corresponding viscosity values, L and H, can be obtained from tables in ASTM D2270 or online calculators.

In summary, the viscosity index (VI) can be calculated using the given formula and specific viscosity values for different temperature points.

Viscosity Index Improver Manufacturers

Some prominent manufacturers of viscosity index improvers include –


Viscosity Index Improver Example

A viscosity index improver is like adding a substance to honey that maintains its thickness at low temperatures but allows it to flow more easily when heated. This helps lubricants maintain consistent viscosity across a range of temperatures.

Viscosity Index Improver Polymer

A viscosity index improver polymer is a sophisticated additive composed of complex polymers. It expands at higher temperatures, enhancing lubricant thickness to maintain stable and consistent viscosity, improving the overall performance of the lubricating oil.

Viscosity Improver Additive

A viscosity improver additive is a substance added to fluids, such as lubricants or oils, to enhance their viscosity stability and performance.

OCP Viscosity Index Improver

OCP (Olefin Copolymer) Viscosity Index Improver is a polymer additive used in lubricating oils to enhance their viscosity index, ensuring better performance across a range of temperatures. It improves the oil’s resistance to thinning at higher temperatures and thickening at lower temperatures.

Best Viscosity Index Improver

Hydrogenated styrene diene copolymer is a widely recognized and effective viscosity index improver in lubricant formulations. Its unique molecular structure enhances viscosity stability across a wide temperature range, making it a preferred choice for improving the viscosity index and overall performance of lubricating oils.

Oil Thickener Additive

Oil thickeners are additives that enhance the viscosity of a liquid or mixture. By increasing thickness, these additives improve lubrication and stability in various applications, such as automotive and industrial processes.

Viscosity Modifiers In Cosmetics

Caprylic Capric Triglyceride is a commonly used viscosity modifier in cosmetics. Derived from coconut oil, it enhances the texture and consistency of skincare products, providing a smooth and luxurious feel without a greasy residue.

Olefin Copolymer Ocp

Olefin Copolymer (OCP) is a type of synthetic polymer formed through the copolymerization of olefin monomers. OCPs exhibit a combination of properties such as durability, chemical resistance, and flexibility, making them valuable in various industrial applications.

Anti Foaming Additives Are Made Of

Anti-foaming additives are often made of silicone-based compounds. These compounds, such as silicone oils or polymers, are effective in reducing or preventing the formation of foam.

Engine Oil Polymer

Engine oil polymers enhance lubricant properties, reducing friction and wear in internal combustion engines. They improve viscosity, stability, and overall performance, ensuring efficient lubrication under varying temperatures and operating conditions.

Engine Oil Polymer
Engine Oil Polymer

1. Viscoplex 8 226

VISCOPLEX® VIIs utilize polymers to enhance viscosity at elevated temperatures while providing minimal impact on viscosity in colder conditions.

These additives find application in formulating multigrade engine oils, transmission fluids, hydraulic fluids, gear oils, and various industrial lubricants, offering advantages such as reduced energy consumption, prolonged service life, and enhanced performance with minimal input.

2. Viscoplex 1 139

VISCOPLEX® pour point depressants (PPDs) by Evonik offer superior wax crystallization control for optimized oil flow in cold climates, ensuring smooth vehicle operation.

Evonik provides customized solutions, technical support, and global logistics flexibility. Their ASTM D 7528 ROBO test aids formulators in developing robust formulations for extreme temperature conditions.

3. Viscoplex 6 850

Evonik’s VISCOPLEX 6 850 enhances driveline fluids, optimizing energy efficiency, reducing torque losses, lowering temperatures, and ensuring extended service life.

4. Viscoplex 7 305

Viscoplex 7 305®-enhanced fluids offer peak viscosity, shear stability, and pump efficiency, optimizing performance across temperatures, enhancing productivity, and reducing energy costs.

Oil Blending Formulation

Lubricant oil blending involves precise addition of base oil components and additives to a mixing kettle, followed by thorough mixing using mechanical or compressed air stirring methods, ensuring product quality through standard analysis.

Viscosity Index Improver In Oil

Viscosity index improvers are additives in oil that enhance its viscosity-temperature relationship, ensuring stable viscosity across a range of temperatures, improving lubrication efficiency and protecting engine components.

Viscosity Index Improver In Oil
Viscosity Index Improver In Oil

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What Is The Significance Of Viscosity?

1. Efficient Lubrication

In lubrication, viscosity is vital for ensuring proper oil film thickness between moving parts. Proper viscosity prevents metal-to-metal contact, reducing friction and wear in engines, gearboxes, and other machinery.

2. Temperature Sensitivity

Viscosity is temperature-dependent, and fluids can change viscosity with temperature variations. Maintaining viscosity within the desired range is critical for consistent performance across different operating temperatures.

3. Fuel Efficiency

In the automotive industry, optimal viscosity in engine oils contributes to fuel efficiency.

Controlling viscosity helps engines operate smoothly, enhancing overall vehicle performance.

4. Hydraulic Systems

Viscosity is crucial in hydraulic fluids to ensure efficient power transmission and control in hydraulic systems.

The right viscosity prevents leakage, cavitation, and excessive friction in hydraulic components.

5. Viscosity Index (VI)

Viscosity Index is a measure of how a fluid’s viscosity changes with temperature.

A higher VI indicates less variation in viscosity with temperature changes, making it important in applications with varying operating conditions.

What Are Pour Point Depressants?

Pour point depressants are additives used in lubricants and fuels to lower the temperature at which the substance solidifies or gels, improving flow properties at low temperatures.

Viscosity Modifiers Engine Oil

Viscosity modifiers are additives in engine oil that enhance its viscosity-temperature relationship. They improve the oil’s flow at low temperatures while maintaining viscosity at high temperatures.

Viscosity Grade Vs Index

Below is a table comparing Viscosity Grade and Viscosity Index:

PropertyViscosity GradeViscosity Index
DefinitionA measure of a fluid’s resistance to flow. It indicates the fluid’s thickness or consistency.A measure of the change in viscosity of a lubricant with temperature.
UnitsTypically expressed in centistokes (cSt) or Saybolt Universal Seconds (SUS).Unitless measure.
ApplicationCommonly used in the automotive and industrial lubricant industry.Used to characterize the viscosity-temperature behavior of lubricating oils.
ScaleMultiple scales exist, such as SAE (Society of Automotive Engineers) for engine oils.Typically ranges from 0 to 100. Higher values indicate a smaller change in viscosity with temperature.
Importance in lubricationImportant for ensuring proper lubrication in different operating conditions.Important for predicting how well a lubricant will perform over a range of temperatures.
Influence of temperatureViscosity grade changes with temperature, affecting the lubricant’s flow properties.Viscosity index reflects how much the viscosity changes with temperature. Higher index indicates less sensitivity to temperature changes.
ExampleSAE 10W-30 (for engine oil)A lubricant with a high viscosity index (VI) is less affected by temperature changes.    

Viscosity Index Chart

Viscosity Index Chart
Viscosity Index Chart

How To Increase The Viscosity Of Oil

The best way to increase the viscosity of oil depends on several factors, including the type of oil, the desired level of increase, and the intended application. Here are some methods you can consider:

1. Physical Methods

  • Cooling: Generally, oils become more viscous as their temperature decreases. If the application allows, simply chilling the oil can be an effective and non-invasive approach.
  • Evaporation: Removing lighter fractions from the oil through evaporation can concentrate the heavier molecules, leading to a thicker consistency.

2. Chemical Methods

Adding thickeners: Various thickening agents, such as polymers, long-chain fatty acids, and nanoparticles, can be mixed with the oil to physically increase its resistance to flow.

Chemical reactions: In some cases, specific chemical reactions can be used to modify the oil’s molecular structure, enhancing its viscosity. This, however, typically requires specialized expertise and equipment.

3. Other Methods

Blending: Mixing high-viscosity oils with lower-viscosity ones can achieve a desired intermediary viscosity. This is common in lubricants where specific viscosity grades are needed.

Shear thickening: Certain materials exhibit thixotropy, where their viscosity increases with applied shear stress. Using such materials as additives can create shear-thickening oils for specific applications.

4. Important Considerations

  • Compatibility: Ensure any thickeners or additives are compatible with the oil and won’t cause unwanted chemical reactions or adverse effects on the application.
  • Food safety: If the oil is intended for food use, choose additives and methods approved for food contact to avoid contamination.
  • Environmental impact: Be mindful of the environmental impact of your chosen method, especially if it involves chemical modifications or waste generation.

How Can I Reduce Viscosity Of Oil?

Here are several methods to reduce the viscosity of oil:

1. Increase Temperature

Heating the oil can significantly reduce its viscosity. As temperature increases, the molecules in the oil move more freely, causing the oil to become less viscous.

2. Additives

Using specific additives can alter the viscosity of oil.

3. Dilution

Mixing the oil with a less viscous solvent or another oil with lower viscosity can reduce the overall viscosity.

4. Mechanical Agitation

Stirring or mechanically agitating the oil can help break down molecular bonds and reduce viscosity. This method may be suitable for small quantities of oil, but it might not be practical for large-scale applications.

5. Pressure Reduction

Lowering the pressure on the oil can decrease its viscosity.

6. Ultrasound Treatment

Ultrasonic waves can be used to break down molecular structures in the oil, leading to a reduction in viscosity.

Viscosity Index Improver How To Use

Here’s a general guide on how to use viscosity index improvers:

Step 1: Determine the Desired Viscosity Range

Understand the temperature range in which your machinery or engine operates. The VI improver is chosen to achieve the desired viscosity within this range.

Step 2: Mixing Process

Viscosity index improvers are typically added to the base oil during the oil blending process. Ensure thorough mixing to achieve a homogeneous blend.

Step 3: Monitoring and Testing

Regularly monitor the viscosity of the oil using appropriate testing methods. Adjust the concentration of the VI improver if necessary to maintain the desired viscosity.


What are viscosity increasing additives?

  • Polymers
  • Cellulose derivatives
  • Clays
  • Polymeric chains
  • Shear-thickening additives

What is viscosity index in motor oil?

The viscosity index (VI) of motor oil tells you how much the oil’s viscosity changes with temperature. In simpler terms, it indicates how well the oil maintains its thickness despite temperature fluctuations.

Does emulsifier increase viscosity?

Yes, emulsifiers can affect viscosity. Emulsions with higher concentrations of emulsifiers (0.55 to 0.7%) tend to exhibit the highest viscosity compared to lower concentrations (0.25 and 0.4%).

What is a good viscosity index?

A viscosity index between 95 and 100 indicates excellent stability of lubricating oil’s viscosity across temperature variations.

What is viscosity index formula?

The viscosity index (VI) is calculated using the formula: VI = (L – H) / (L – 100), where L and H are the viscosities at 40°C and 100°C, respectively.

How viscosity index of oil can be improved?

To enhance the viscosity index of oil, additives such as viscosity index improvers are commonly employed, reducing sensitivity to temperature changes and improving overall lubricating performance.

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Viscosity index improvers play a crucial role in enhancing the performance and stability of lubricants across a wide range of temperatures. By effectively minimizing the effects of viscosity changes, these additives ensure consistent and reliable lubrication, thereby prolonging the lifespan of engines and machinery.

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