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Fleet customers demand reduced operating costs. This necessitates the development of engine oils which can provide maximum fuel economy and extended oil drains, while still maintaining engine durability. This is particularly important in diesel engines produced since October 1998. These engines use retarded timing to meet EPA's emission requirements and, as a consequence in some cases, generate high soot levels in the engine oil. Extended oil drains in 1995 Caterpillar 3406E and 1996 Detroit Diesel Series 60 engines found no statistical difference in fuel economy or wear between a synthetic SAE 5W-40 and an SAE 15W-40 using API Group II base stocks. Both oils had the same API CG-4/SJ quality level. Soot levels at oil drains of 40,000-50,000 miles (64,372 - 80,465 km) ranged from 0.5-1.2%.

Bearing capability of one million miles has been demonstrated in line-haul truck operations with Cummins, Detroit Diesel, Caterpillar and Mack Truck engines. Bearing failure analysis helped to define the requirements for long service bearings, in terms of the appropriate oil and bearing quality, and proper maintenance practice. Surface science instrumentation was used for failure analysis, since visual observations alone cannot provide a definitive answer. This paper should help prevent bearing failures in the future and enable others to identify the failure mode correctly and quickly.

With the drive to reduce emissions and improve fuel economy, fuel injection pressures have increased. This has increased Hertzian stresses on the roller follower cam system to the point that cam lobe contact fatigue failure has become the “Achilles heel” of diesel engine durability in the 1990s. Contact fatigue failures have occurred on both injector lobes and the exhaust and inlet lobes. This is particularly the case in fleets with frequent engine shut downs and starts, stop-go service and in some line-haul fleets. This paper describes field service cam failures across several engine types and applications. In our experience supporting fleet customers in cam failure analysis, we found that a combination of ten critical independent variables must be correct in order to prevent cam lobe contact fatigue failures. These variables are each discussed separately.