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Global Heavy Duty Diesel engine emission legislation requires stepwise reduction of NOx and particulate emissions between 1989 and 2009. Today, most US diesel engine manufacturers are incorporating cooled Exhaust Gas Recirculation (EGR) and retarded engine timing as a means of reducing NOx emission. This has resulted in higher levels of soot being present in used oils. The first part of this paper builds on previous work with fresh oils and describes a study of the effect of highly sooted oils on low temperature pumpability in diesel engines. Experimental SAE 15W-40 Heavy Duty Diesel Oils (HDDO), formulated with different Viscosity Index Improver (VII) chemistries, were run in a Mack T-8 engine to obtain a soot level of approximately 6.5%. These sooted oils were then evaluated in a Cummins M11 engine installed in a low temperature chamber. Times to lubricate critical engine components were measured at temperatures ranging between -10 °C and -20 °C.