Key Points and Differences in Shear Stability Rating Criteria for Engine Oils Containing Polymers

Lubricant viscosity index improvers are becoming common additives to improve the viscosity index, low temperature fluidity and high temperature viscosity retention of lubricants. Viscosity index improvers are typically oil-soluble polymers that are subject to shear and pyrolysis during engine operation, resulting in fracture of the macromolecules and a significant reduction in the thickening capacity of the fractured polymer and a reduction in the viscosity of the oil. Commonly used viscosity index improvers are polymethacrylate (PMA), ethylene propylene copolymer (OCP), hydrogenated styrene isoprene copolymer (SV), polyisobutylene (PIB) four categories. Ethylene propylene copolymer (OCP) is widely used in lubricants because of its better performance and price.

The next section describes the key points and differences in shear stability measurement standards for in-use engine oils.

Ultrasonic Shear Stability Determination Method

SH/T 0505-92 Shear stability of polymer-containing oils is similar to ASTM D2603-01 (13) Standard Test Method for Sonic Shear Stability of Polymer-Containing Oils (ultrasonic shear stability of polymer-containing oils), both methods Both methods use an ultrasonic oscillator to evaluate the loss of viscosity caused by ultrasonic shear, and the rate of loss of viscosity at 40°C is used to evaluate the shear stability of polymer-containing oils.

However, ASTM D2603 has undergone several adjustments, and the measurement conditions and calibration methods have changed significantly. astm d2603-01(13) specifically states that due to the limitations of this method, it is not applicable to the determination of engine oil shear stability.

Fuel Nozzle Shear Stability Determination Method

ASTM D6278-17e1, ASTM D5275-03, CEC L-14-A-93, ASTM D7109-12, SH/T 0107-2007, DIN 51382, CEC L-14-A-93, ISO 20844-2015, etc. are all used to determine the shear stability of lubricants by the fuel nozzle shear method.

ASTM D6278-17e1 and ASTM D5275-03 are derived from the obsolete ASTM D3945-86. ASTM D6278-17e1, CEC L-14-A-93, ASTM D7109-12, SH/T 0107-2007, DIN 51382, ISO 20844-2015, etc. are all using Bosch diesel nozzle, while ASTM D5275 uses Waukesha diesel nozzle and the measured results will be different from other methods.

ASTM D6278-17e1 specifies that the results measured by this method do not correlate with those measured by ASTM D2603. ASTM D6278-17e1 has the same equipment as CEC L-14-A-93, and the difference with CEC-L-14-A-93 is the calibration period. The difference with the obsolete ASTM D3945 is in the calibration and operation methods.

ASTM D7109 is similar to ASTM D6278, but requires 30 and 90 cycles, whereas ASTM D6278 requires only 30 cycles.

Conclusion

1, ultrasonic shear stability measurement method has not been applied to engine oil.

2, diesel nozzle shear stability method is applicable to the determination of engine oil, is generally accepted method, but there are more standards, should pay attention to the screening.

3, the latest method for evaluating the shear stability of polymer-containing lubricants, especially engine oils, is ASTM D6278 and ASTM D7109. for long drainage period requirements, ASTM D7109 emphasizes the determination of shear stability for 30 and 90 cycles.


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