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Diesel particulate filters are remarkably efficient in reducing emissions of particulate matter from heavy-duty diesel engines. However, their efficiency and performance are negatively impacted by contaminants derived from consumed engine lubricant. This accumulation of incombustible ash imparts a fuel economy penalty due to increased system backpressure and demand for more frequent regeneration events. This study documents a systematic evaluation of lubricant impacts on DPF ash loading, system performance, and fuel economy. A novel, ultra-low ash heavy-duty engine oil demonstrates significant advantages in aged systems when compared to tests using conventional lubricants. The ultra-low ash oil yields a significantly lower ash loading that is also more dense therefore offering extended DPF maintenance interval and potential for 3% fuel economy retention benefit. These advantages offer potential for significant reduction in cost to operate and maintain a DPF equipped engine.

Due to engine oil consumption, over 90% of the incombustibles in the diesel particulate filters (DPF) are derived from organometallic lubricant additives. These components are derived from calcium and magnesium detergents, zinc dithiophosphates (ZnDTP) and metal-containing oxidation inhibitors. They do not regenerate as they are non-volatile metals and salts. Consequently, the DPF has to be removed from the vehicle for cleaning. Ashless oil could eliminate the need for cleaning. This study initially focused on development of an ashless oil, but eventually concluded that this oil could not meet the valve-train wear requirements of the API CJ-4, SN/ACEA E9 oil categories. However, a zero-phosphorus oil with no ZnDTP and an extremely low sulfated ash of 0.4% demonstrated that it could meet critical engine tests in API CJ-4/ACEA/SN. The above oil, which has been optimized at 0.3% sulfated ash, has proven field performance in Cummins ISX with DPF using ultra low sulfur diesel (ULSD).

The continuing push for improved fuel economy, reduced carbon emissions, and lower operating costs has resulted in higher operating temperatures for axle lubricants in passenger cars and commercial vehicles. These higher operating temperatures, in turn, have placed more severe demands on the thermal & oxidative performance of axle lubricants. A number of industry-standard, laboratory methods exist to evaluate this key performance parameter. This paper discusses the use of laboratory methods to evaluate oil service life. We examine the behavior of five commercially available axle lubricants in the CEC L-48 oxidation test (Apparatus A). The oils were chosen so that different additives and base oils could be compared. We evaluated both the effect of time and temperature on the oxidation behavior. In agreement with previous studies, we found that infrared (IR) spectroscopy provides a convenient and meaningful way to track the extent of oxidative degradation.

By 2014, all new on- and off-highway diesel engines in North America, Europe and Japan will employ diesel particulate filters (DPF) in the exhaust in order to meet particulate emission standards. If the pressure across the DPF increases due to incombustibles remaining after filter regeneration, the exhaust backpressure will increase, and this in turn reduces fuel economy and engine power, and increases emissions. Due to engine oil consumption, over 90% of the incombustibles in the DPF are derived from inorganic lubricant additives. These components are derived from calcium and magnesium detergents, zinc dithiophosphates (ZnDTP) and metal-containing oxidation inhibitors. They do not regenerate as they are non-volatile metals and salts. Consequently, the DPF has to be removed from the vehicle for cleaning. Ashless oil could eliminate the need for cleaning.

The Viscosity Index (VI), now defined by ASTM D 2270, is a relative number intended to represent the degree of change in viscosity versus temperature for lubricating oils. The basis for the rating scale, which was first defined in 1929, is a comparison of a candidate oil with two reference oils, one defined as “100 VI” and the other defined as “0 VI”. The VI scale has been widely used since its inception because of its simplicity and good correlation to a number of physical and chemical properties. However, the rating method suffers from a number of fundamental problems which are not realized by most users of the method today. This paper examines the assumption basis and historical development of the VI scale with an emphasis on the arbitrary and non-systematic manner in which the “100 VI” and “0 VI” reference series have been defined and modified over the years.