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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.

In order to meet the U.S. EPA's 2007 on-highway emission standards for particulate and NOx, all diesel engines will require diesel particulate fi lters (DPFs) and cooled exhaust gas recirculation (EGR) and will utilize ultra-low sulfur fuel. As this will be the first time that all on-highway diesel engines will employ DPFs combined with ultra-low-sulfur fuel, the Engine Manufacturers Association (EMA) requested that a new oil category be developed to provide compatibility with DPFs in the exhaust system, as well as engine durability for both new and legacy engines. This paper reviews the development of this new oil category called API CJ-4, which will be introduced in October 2006. This diesel engine oil category is the first in the U.S. which limits the oil's sulfated ash, phosphorus, and sulfur in order to insure adequate service life of the DPF. The API CJ-4 oil category includes 9 fi red engine tests and 6 bench tests.