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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.

A simplex statistical design was used to model the Sequence VE engine performance of two dispersants, P and L, in a lubricant formulation. Dispersant P is a polyisobutylene succinimide, and L a low molecular weight ethylene propylene succinimide dispersant. The model showed that in the Sequence VE test, dispersant L gives superior sludge and varnish performance as compared to dispersant P. Furthermore, there is a synergism in the Sequence VE sludge performance when the two dispersants are mixed in the formulation.