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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 API has established lubricant specifications, which include standard tests for ring and liner wear. The Mack T-10 is one such test, performed on a prototype engine with Exhaust Gas Recirculation (EGR). At EOT, the liner wear is measured by profilometry, while the ring wear is measured by weight loss. It was decided to monitor the wear of the rings and liners during a full-length T10 test in order to observe the evolution of the wears and wear rates over the course of the test, by using the Surface Layer Activation (SLA) and Bulk Activation (BA) techniques. Three different radioisotopes were created, one in the liners at the turnaround zone, one in the chromium-containing coating on the ring faces, and one in the iron bulk of the rings. This enabled us to observe the wear characteristics of these three components separately. In particular, we were able to separate the face and side ring wears, which cannot be done with simple weight-loss measurements.

More stringent emission legislation has been a driver for changes in the design of Heavy Duty Diesel engines since the 1980s. Significant gains have been made over the years but, in 2007 and again in 2010, diesel engines in North America will have to meet even more stringent requirements for particulate matter and nitrogen oxide emissions. A reduction of the sulfur level in diesel fuel to a maximum of 15 mg/kg has been mandated as an enabler for new diesel engine exhaust gas after-treatment systems. Many studies have been published on the impact of the use of low sulfur diesel fuel. The focus of most of these studies has been on the possible impact on exhaust gas after-treatment system durability, but little has been documented on lubricant degradation and on the long term impact on engine durability. The objectives of the field test discussed in this paper were to evaluate the impact of low sulfur fuel and of a reduction in the TBN of the lubricant on lubricant degradation.

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant.

Increasingly severe emission legislation for heavy duty diesel engines has forced engine builders to modify their engine designs dramatically over the last few years. Some of the design modifications, such as the retardation of injection timing, resulted in higher levels of soot contamination of the crankcase lubricant. Consequently, higher wear levels were observed in the engines as a result of soot abrasion. Despite the more severe environment, there is a demand for increased engine life, which necessitates the search for ways to reduce wear. This paper describes the results of several wear studies in diesel engines. Valve train wear in engines producing high soot levels in the crankcase oil appears to be a function of soot dispersion and anti-wear film formation. Reducing the abrasiveness of the soot agglomerates and increasing the anti-wear film formation rate both result in lower valve train wear levels.

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.

Advancement in Heavy Duty Diesel Engine Oils has, for approximately two decades, been driven by the ever more stringent emission legislation for NOx and Particulates. Over the last few years, the focus has shifted to reducing CO2 emissions and reducing operating cost by improving the engine's fuel economy. With fuel economy as an important new technology driver, the industry is exploring and introducing diesel engine oils of viscosity grades that used to be applied solely in passenger car engines, such as SAE 10W-30 and even SAE 5W-30. To avoid misapplication, API has decided that heavy duty diesel engine oils, most of which are formulated close to the maximum 0.12% phosphorus limit in the API C specification, can no longer add the API S gasoline engine claim.

Advancement in Heavy Duty Diesel Engine Oils has, for approximately two decades, been driven by the ever more stringent emission legislation for NOx and Particulates. Over the last few years, the focus has shifted to reducing CO2 emissions, which created an interest in fuel efficient lubricants. In addition, increased fuel cost and a need to control operational expenses in a weaker economy have further heightened the interest in fuel efficient lubricants. Where the trucking industry was reluctant to move away from the tried and true SAE 15W-40 viscosity grade, there is now a strong interest in pushing the boundaries of lower viscosity to reduce internal friction in the engine and thereby improve fuel efficiency. Consequently, the industry is exploring and introducing lower viscosity grades, such as SAE 10W-30 and even SAE 5W-30.

More stringent emission legislation has been a driver for changes in the design of Heavy Duty Diesel engines since the 1980s. Optimization of the combustion processes has lead to significant reductions of exhaust emission levels over the years. However, in the year 2002, diesel engines in the USA will have to meet an even more stringent set of emission requirements. Expectations are that this will force most engine builders to incorporate Exhaust Gas Recirculation (EGR). Several studies of the impact of EGR on lubricant degradation have shown increased levels of contamination with soot particles and acidic components. Both of these could lead to changes in lubricant requirements. The industry is developing a new specification for diesel engine lubricants, PC-9, using test procedures incorporating engines with EGR.