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The ASTM Sequence VE test was developed to provide better discrimination than the ASTM Sequence V-D test when measuring the ability of oils to prevent sludge and varnish deposits and valve train wear. It is a key test in the definition of API SG oils. The formulation of API SG oils which provide superior performance as measured by the Sequence VE test depends largely on the type of dispersant which is used. By using statistical design methods in the synthesis of dispersants, the best dispersant can be defined in an efficient, cost-effective manner. In order to develop a succinimide dispersant which could provide API SG performance, experimental design techniques were successfully used to optimize the experimental parameters. In the half replicate of a 23 or a Taguchi L4 design which was used, the three parameters selected were: two levels of dispersant molecular weight, two methods of derivatizing, and two types of amine.

Engine oil viscosity loss was investigated in highway service and in ASTM D-3945 Procedure A (diesel injector) shear stability test. The six oils involved contained various viscosity index improvers and had D-3945 100°C kinematic viscosity losses ranging from low to high. The losses in service were highest for an oil with one of the lowest D-3945A viscosity losses. D-3945A also did not correlate with service using 150°C high shear viscosity losses. D-3945A shearing severity was modified over a wide range, but it still did not rank oils like highway service. Results indicate a need for a more meaningful viscosity-loss bench test.