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Changing diesel engine emission requirements for 2002 have led many diesel engine manufacturers to incorporate cooled Exhaust Gas Recirculation, EGR, as a means of reducing NOx. This has resulted in higher levels of soot being present in used oils. This paper builds on earlier work with fresh oils and describes a study of the effect of highly sooted oils on the low temperature pumpability in diesel engines. Four experimental diesel engine oils, of varying MRV TP-1 viscosities, were run in a Mack T-8 engine to obtain a soot level ranging between 6.1 and 6.6%. These sooted oils were then run in a Cummins M11 engine installed in a low temperature cell. Times to lubricate critical engine components were measured at temperatures ranging between -10 °C and -25 °C. A clear correlation was established between the MRV TP-1 viscosity of a sooted oil and the time needed to lubricate critical engine components at a given test temperature.

A series of SAE 5W-30 and SAE 10W-30 engine oils was evaluated in a New York City taxi fleet to study the performance of prototype API SG engine oils. Key formulation variables studied were SAE viscosity grade and Viscosity Index improver chemistry. A good correlation was established between Sequence VE sludge and varnish results and field performance. The deposit control value of dispersant Viscosity Index improvers was demonstrated. Formulations based on polymethacrylate Viscosity Index improvers performed directionally better in the field than the Sequence VE results predicted. Overall, the field performance of API SG quality oils was excellent.

An ASTM Task Force was formed in 1979 to improve the discriminatory abilities for engine sludge deposits and valve train wear of the ASTM Sequence V-D test. Several statistically designed programs were conducted to identify procedural and hardware items to achieve the stated objectives. The 2.3 liter, four cylinder test engine was updated with electronic fuel injection and high swirl combustion chamber technology. Of the parameters evaluated, increased test length, adjustments of temperatures and control of the rocker cover temperature had the greatest impact on increased test severity. A procedure has been developed that better discriminates between known good and poor engine oils. Field correlation has been improved and expanded to include European experience. An extensive program has been planned to establish field correlation and test precision.