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This paper is first in a series of papers designed to investigate wear processes in modern heavy duty diesel engines. The objective of the series is to discuss the effects that engine drive cycle, lubricant formulations and in-service ageing of lubricants have on wear of critical engine components. In this paper, the Radioactive Tracer Technology technique was used to study the steady state wear behavior of a number of contacting surfaces in a Caterpillar 1P engine, as a function of the drive cycle. A test protocol consisting of 7 modes or stages was used to simulate a variety of drive cycles. The results from this work provide useful insights into the wear behavior of these surfaces under a variety of speed and load conditions.

This paper investigates the phenomena of gel formation and poor filtration performance of engine oils containing certain olefin copolymer (OCP) viscosity modifiers (VMs). Low temperature pilot plant and bench scale filtration tests have been used to study the filtration behaviors of a wide range of low-ethylene and high-ethylene OCP VMs at various temperatures but with particular focus on the performance at 0°C. Further, rheological studies have been carried out on fully formulated oils as well as on PAO solutions of these polymers to understand the effect of thermal history on the polymer solution behavior over a broad range of temperatures. These studies suggest that many high-ethylene OCPs are prone to the formation of polymer aggregates in oil solutions. Long crystalline polyethylene segments present in high-ethylene OCP molecules are believed to interact with similar segments in neighboring molecules, leading to the formation of aggregates.

Low temperature pumpability has been an important requirement of engine oils for the past two decades. However, until recently this requirement has applied only to fresh oils. Pumpability can deteriorate significantly during oil's life cycle in the engine. Many factors such as combustion byproducts and oxidation can influence oil pumpability at low temperatures. This paper examines the effects of in-service aging on low temperature pumpability of oils using a variety of industry and proprietary engine tests. In particular, the paper investigates the role of viscosity modifiers in the retention of satisfactory low temperature performance in service. The data show that oils formulated with certain types of viscosity modifiers tend to maintain robust low temperature pumpability throughout their entire stay in the crankcase. Lubricants formulated with another class of viscosity modifiers tend to lose their low temperature performance quite early in their life cycle in the engine.