How to choose engine viscosity index improver(VII)? Pros, Cons, & Applications of the 4 major VIIs.

What's the viscosity index of lubricant oil? 

The viscosity of lubricant is influenced by temperature: the higher the temperature, the lower the viscosity.

The viscosity of oil indicates the degree of viscosity at different temperatures.

 

 

Viscosity is divided into dynamic viscosity and kinematic viscosity.

Dynamic viscosity (absolute viscosity) reflects the force required to make the lubricant flow. And the kinematic viscosity reflects the flow speed of the lubricant under force.

 

What's the difference between high and low viscosity index (VI)?

Viscosity index reflects the stability of the lubricant oil viscosity with temperature.

The higher the viscosity index, the more stable the oil viscosity with temperature.

The lower the viscosity index, the greater the viscosity fluctuation under temperature changes.

In the engine oil, the high and low of viscosity index will influence the cold-start, high temperature protection, oil film strength, and energy saving performance.

The influence of overly high or too low engine oil viscosity. 

• If the oil viscosity is too high, it will cause:

1. The engine starts with difficulty at low temperatures.
2. It will accelerate parts during start.
3. Large power loss
4. Poor cleaning effect
5. Poor cooling effect

• If the oil viscosity is too low, it will cause:

1. It's easy to damage the oil film
2. Poor sealing effect
3. Large energy oil consumption

 

Therefore, instead of choosing engine oil for different grades of oil according to the working conditions, choose the proper engine oil based on the basis of the seasonal and area temperature conditions. This can guarantee the normal operation and good lubricant condition.

 

The choice and application of VII in engine oil

Why should engine oil use viscosity index improvers?

VII is one of the indispensable core additives in modern multi-grade engine oil; it makes the engine oil an all-weather and automatic lubricant product, and it's the key technology that ensures the engine's stable operation under the requirements of high performance, low emission, and long lifespan.

 

The types of viscosity index modifiers and their differences.

The viscosity index modifiers mainly divide into Polymethacrylate (PMA), hydrostyrene copolymer (HSD), polyisobutylene (PIB), ethylene propylene copolymer (OCP), styrene polyester, and polyn-butyl vinyl ether.

 

• Polymethacrylate (PMA)--suitable for low-temperature formulation.

Polymethacrylate (PMA) has a better viscosity temperature performance and oxidation stability. It has a poor thickening capacity, so a large amount of PMA is needed to formulating multi-grades engine oil that has a high demand for low temperature performance.

Thickening capacity is very important for a viscosity index improver. The stronger thickening capacity of the VII, the less use, and the cost of multi-grade lubricant is lower.

 

The thickening capacity ranking of the 4 main VII is HSD≈OCP >PIB>PMA.

 

PMA Viscosity Index Improver (VII) T602HB is suitable for low viscosity engine oil and has a good thickening capacity, which can improve the viscosity index effectively.

In the meantime, it has a certain effect of reducing the pour point depressant that can promote the low temperature performance.

 

• Ethylene propylene copolymer (OCP)--suitable for multi-grade engine oil, high cost performance.

At present, ethylene propylene copolymer (OCP) is the most widely used VII, and has a high proportion in multi-grade engine oil and industrial oil.

OCP has a strong thickening capacity, good shear stability, good thermal oxidation stability, and is compatible with base oil. It can be applied in engine oil, hydraulic oil, and industrial oil.

 

OCP has a high cost performance, making it the most commonly used VII owing to its comprehensive performance and cost advantage.

 

• Hydrostyrene copolymer (HSD)--suitable for the engine oil that has a high demand for shear stability.

HSD Viscosity Index Improver T7700 hydrostyrene copolymer (HSD) has excellent shear stability, viscosity increasing, and thermal oxidation stability. HSD T7700 also has a low effect on the low temperature performance of base oil, and can adaptto the requirements of multi grades engine.

HSD T7700 is used in high-grade lubricant oil, especially for multi-grade oil of large viscosity span, and it's one of the mainstream viscosity index modifiers.

 

• Polyisobutylene (PIB)--suitable for gear oil, hydraulic oil, and high temperature demands conditions.

Polyisobutylene (PIB) has good high-temperature shear stability and high-temperature oxidation stability; it's suitable for formulating hydraulic oil and multi-grade gear oil.

PIB can keep the molecular structure complete under the condition of extremely high shear ability, and it's not easily degraded at high temperatures, making it suitable for heavy-duty mechanical oil. It has strong stability and is less likely to cause sludge stability or sedimentation.

It is the preferred viscosity index agent for high shear and high temperature stable industrial oil.

 

Chorus lubricant additive company provides a series of viscosity index agents for lubricant oil.

Contact us know more about viscosity index improvers.