http://hrcak.srce.hr/file/37720
"ENGINE OIL VISCOSITY INDEX IMPROVER BEHAVIOUR AT EXTENDED SHEAR STABILITY TEST"
From February 2008, so it's very recent. The gist of this is that two common types of VIIs (Polymethacrylates (PAMA) and Hydrogenated styrene-diene copolymers) used in motor oils failed the 90 cycle shear stability requirement and only one type (Olefin copolymers (OCP)) passed.
Quote:
For determining shear stability we use DIN 51382 method which is also accepted by CEC as the CEC L-14-A-93 method and by ASTM as the ASTM D 6278 method. These are a part of the international specifications for engine oils. The viscosity loss
due to shear stresses is normally determined after 30 cycles of oil passing through the nozzle.
During engine oils application, its viscosity is decreased due to polymer break down of the viscosity index improvers which reduces oil film thickness and causes undesirable phenomena of friction and wear. For this reason, specifications for
engine oils containing polymer additives, define the minimal value of kinematic viscosity after shearing (Table 1) [5].
The manufacturers of vehicles and equipment OEM (Original engine manufacturer) pointed out that the current test for shear stability of engine oils at high loaded diesel engines does not provide satisfactory results and therefore there is not sufficient equipment protection while under application. They believe that this is a consequence of high sliding speeds, heavy loads and high working temperatures where the oil is exposed to the high shear which results in viscosity loss, reduced the oil film thickness and impaired lubrication. The oil does not provide a sufficient viscosity for the engine protection.
In order to find a suitable solution, it has been proposed to perform shear stability testing with already known Orbahn Diesel Injector apparatus. An agreement is reached to expend testing from 30 cycles to 90 cycles which would be better comparable to conditions in practical application.
The new ASTM D 7109 method for shear stability testing has been established which differs in more testing cycles and sample quantity than the previous ASTM D6278 [6,7].
By introduction of the new ACEA (Association des Constructeurs Européens d'Automobiles) and API (American Petroleum Institute) specifications, the changes in requirements for determining shear stability of engine oils aroused. The new ACEA E6-04 and E7-04 specifications than API CI-4 Plus and API CJ-4 set more stringent requirements for the shear stability with the use of the same method, but with 90 cycles instead of the previous 30 cycles of testing [5].
Apart from ACEA and API specifications, determining shear stability of oils with 90 cycles tests, is also required by some engine and vehicle manufacturers, for example, Mercedes-Benz – all the specifications, Volvo for VDS-3 and VDS-4 and other manufacturers in relation to ACEA and API specifications.
All of them require that kinematic viscosity at 100 °C after shearing remains within SAE J300 classification grades (Table 1).
Quote:
Results
The test results show the expected degradation of tested oils due to decrease of kinematic viscosity (Figure 4).
The samples B1, B2, B3 and B4 based on OCP show very good stability to shear stresses and they meet the requirements of the shear stability with 90 cycles of testing, i.e. the engine oil remains within viscosity grade.
The samples A and C, which met the specification requirements with 30 cycles of testing, after testing shear stability with 90 cycles show the kinematic viscosity loss under the limit value of 12,5 mm2/s. Therefore they do not meet the requirements
of the new specifications of engine oils.
After extension of testing, kinematic viscosity loss of sample A is not large and amounts 0,18 mm2/s (Figure 5). In order to achieve the minimal kinematic viscosity required by the new engine oil specifications, the initial kinematic viscosity at 100 °C should be increased for oils mixed with the viscosity index improvers based on polymethacrylates.
The sample C has shown a great viscosity loss after being tested with 90 cycles. That loss is 1,09 mm2/s, which is significantly more than with other samples where it amounts 0,18 – 0,28 mm2/s (Figure 5). This shows that the viscosity index
improvers based on styrene-isoprene are not suitable for formulating the most demanding engine oils.
The test results demonstrate that the oils formulated with inappropriate viscosity index improvers are not able to provide the proper protection of an engine.
Quote:
Conclusions
1. New international specifications ACEA and API require that the shear stability of
engine oils is tested by 90 cycles of oil passing through the nozzle instead of
current 30 cycles; these requirements are accepted by a number of vehicle
manufacturers.
2. Shear stability determination according to new ASTM D 7109 method has been
defined with 90 cycles of testing.
3. Different concentrations of viscosity index improvers are needed for production
of multigrade engine oil of the same viscosity; the highest additive concentration
is needed for the viscosity index improvers based on OCP.
4. Viscosity index improvers based on OCP have the best shear stability after 90
cycles of testing.
5. Engine oil with the viscosity index improver based on styrene-isoprene (C) has a
significant viscosity loss after extended testing from 30 cycles to 90 cycles and it
does not meet requirements of the new international and OEM specifications.
"ENGINE OIL VISCOSITY INDEX IMPROVER BEHAVIOUR AT EXTENDED SHEAR STABILITY TEST"
From February 2008, so it's very recent. The gist of this is that two common types of VIIs (Polymethacrylates (PAMA) and Hydrogenated styrene-diene copolymers) used in motor oils failed the 90 cycle shear stability requirement and only one type (Olefin copolymers (OCP)) passed.
Quote:
For determining shear stability we use DIN 51382 method which is also accepted by CEC as the CEC L-14-A-93 method and by ASTM as the ASTM D 6278 method. These are a part of the international specifications for engine oils. The viscosity loss
due to shear stresses is normally determined after 30 cycles of oil passing through the nozzle.
During engine oils application, its viscosity is decreased due to polymer break down of the viscosity index improvers which reduces oil film thickness and causes undesirable phenomena of friction and wear. For this reason, specifications for
engine oils containing polymer additives, define the minimal value of kinematic viscosity after shearing (Table 1) [5].
The manufacturers of vehicles and equipment OEM (Original engine manufacturer) pointed out that the current test for shear stability of engine oils at high loaded diesel engines does not provide satisfactory results and therefore there is not sufficient equipment protection while under application. They believe that this is a consequence of high sliding speeds, heavy loads and high working temperatures where the oil is exposed to the high shear which results in viscosity loss, reduced the oil film thickness and impaired lubrication. The oil does not provide a sufficient viscosity for the engine protection.
In order to find a suitable solution, it has been proposed to perform shear stability testing with already known Orbahn Diesel Injector apparatus. An agreement is reached to expend testing from 30 cycles to 90 cycles which would be better comparable to conditions in practical application.
The new ASTM D 7109 method for shear stability testing has been established which differs in more testing cycles and sample quantity than the previous ASTM D6278 [6,7].
By introduction of the new ACEA (Association des Constructeurs Européens d'Automobiles) and API (American Petroleum Institute) specifications, the changes in requirements for determining shear stability of engine oils aroused. The new ACEA E6-04 and E7-04 specifications than API CI-4 Plus and API CJ-4 set more stringent requirements for the shear stability with the use of the same method, but with 90 cycles instead of the previous 30 cycles of testing [5].
Apart from ACEA and API specifications, determining shear stability of oils with 90 cycles tests, is also required by some engine and vehicle manufacturers, for example, Mercedes-Benz – all the specifications, Volvo for VDS-3 and VDS-4 and other manufacturers in relation to ACEA and API specifications.
All of them require that kinematic viscosity at 100 °C after shearing remains within SAE J300 classification grades (Table 1).
Quote:
Results
The test results show the expected degradation of tested oils due to decrease of kinematic viscosity (Figure 4).
The samples B1, B2, B3 and B4 based on OCP show very good stability to shear stresses and they meet the requirements of the shear stability with 90 cycles of testing, i.e. the engine oil remains within viscosity grade.
The samples A and C, which met the specification requirements with 30 cycles of testing, after testing shear stability with 90 cycles show the kinematic viscosity loss under the limit value of 12,5 mm2/s. Therefore they do not meet the requirements
of the new specifications of engine oils.
After extension of testing, kinematic viscosity loss of sample A is not large and amounts 0,18 mm2/s (Figure 5). In order to achieve the minimal kinematic viscosity required by the new engine oil specifications, the initial kinematic viscosity at 100 °C should be increased for oils mixed with the viscosity index improvers based on polymethacrylates.
The sample C has shown a great viscosity loss after being tested with 90 cycles. That loss is 1,09 mm2/s, which is significantly more than with other samples where it amounts 0,18 – 0,28 mm2/s (Figure 5). This shows that the viscosity index
improvers based on styrene-isoprene are not suitable for formulating the most demanding engine oils.
The test results demonstrate that the oils formulated with inappropriate viscosity index improvers are not able to provide the proper protection of an engine.
Quote:
Conclusions
1. New international specifications ACEA and API require that the shear stability of
engine oils is tested by 90 cycles of oil passing through the nozzle instead of
current 30 cycles; these requirements are accepted by a number of vehicle
manufacturers.
2. Shear stability determination according to new ASTM D 7109 method has been
defined with 90 cycles of testing.
3. Different concentrations of viscosity index improvers are needed for production
of multigrade engine oil of the same viscosity; the highest additive concentration
is needed for the viscosity index improvers based on OCP.
4. Viscosity index improvers based on OCP have the best shear stability after 90
cycles of testing.
5. Engine oil with the viscosity index improver based on styrene-isoprene (C) has a
significant viscosity loss after extended testing from 30 cycles to 90 cycles and it
does not meet requirements of the new international and OEM specifications.
