OCP VII in Engine Oils: Thickening Efficiency vs. Shear Stability

In modern multigrade engine oil formulations, ethylene-propylene copolymer (OCP) viscosity index improvers (VIIs) have a dominant position in the internal combustion engine oil market due to their excellent cost-performance ratio.

Thickening ability and shear stability are mutually exclusive and must be balanced according to the application scenario.

 

Why OCP can improve engine oils' viscosity-temperature performance of?

One of the development trends for modern internal combustion engine oils is multigrade oils, which is suitable for a wide temperature range viscosity requirements.

OCP viscosity index improver as a lubricant additive, owing to its low cost, excellent viscosity-temperature performance and thickening power is widely used in engine oils.

It can be also used for the ideal choice for multi-grade engine oils.

 

OCP viscosity index improver is a high molecular weight polymer with identical chain structure but different chain lengths. When dissolved in engine base oil, the high molecular weight chain of OCP will change with temperature.

At low temperatures, the molecular chains contract and coil, has a low thickening ability to avoid excessive low-temperature viscosity and ensuring good engine cold-start performance.

At high temperatures, the chains fully extend, has a high thickening efficiency, to maintain a the lubricating film stable at high temperatures.

 

The viscosity-temperature performance of OCP is related to its thickening efficiency and shear stability.

 

Factors affecting thickening efficiency

Thickening efficiency is mainly dependent on the molecular weight, the number of main chain carbon atoms (–CH₂–), and its conformation in the base oil.

The thickening efficiency of OCP is primarily determined by molecular weight. Higher molecular weight leads to a larger effective molecular volume and greater intermolecular chain friction, thus contributing more to the oil's viscosity.

Because the carbon atoms of ethylene propylene copolymers is located in the main chain, OCP VII exhibit the strongest thickening power.

As shown in the picture, to achieve the same thickening efficiency in formulating a multigrade oil, the required of OCP is the lowest; PMA requires about 2 to 3 times the amount of OCP.

 

Considering OCP's excellent performance in shear stability, high-temperature and high shear (HTHS), etc., OCP viscosity index modifier is widely used in multigrade oil, which can reduce raw material costs .

Molecular weight distribution also affects thickening ability: a narrower distribution generally provides more concentrated and stable thickening efficiency.

 

Therefore, high-molecular-weight, narrow-distribution OCP products have a distinct advantage in thickening efficiency.

 

Low-temperature performance

In addition to consider thickening efficiency and shear stability, low-temperature performance is also a critical factor in formulation design.

Cold Cranking Simulator (CCS) and Mini-Rotary Viscometer (MRV) are two key indices for evaluating the low-temperature performance of engine oils.

Comparison of thickening efficiency, shear stability, and low-temperature performance

It is clear that no single product can satisfy all requirements for thickening efficiency at the same time, shear stability, and low-temperature performance.

 

Chorus OCP viscosity index improver recommended

 

Chorus OCP viscosity index improvers J0050 and J0010 are ideal thickening agents for improving lubricant performance.

With their excellent properties, they serve as viscosity thickeners for engine oils, providing better shear stability and low temperature performance for passenger car motor oils and heavy duty diesel engine oils. When combined with a suitable pour point depressant, OCP J-0050 VII can also improve pour point characteristics, further enhancing engine oil performance.

 

Chorus is a professional viscosity index improver supplier. We also offer you PMA viscosity index improvers including star-block type PMA VII, and HSD viscosity index improvers widely used in wide range multigrade engine oils.

 

We can recommend the most suitable VI improver products based on your operating conditions and requirements.

Contact us for the latest product information and quotations.