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Because of the rising costs of engine tests, bench testing is a necessity in engine oil development. Which bench test to use remains a problem. Recently, we have reported on the use of electrical contact resistance (ECR) coupled with a ball-on-disk tribometer to study the formation and the durability of antiwear films from binary additive mixtures. This paper extends the ECR study to fully formulated fresh oils run in both fired gasoline engines and the ECR bench test. X-ray Photoelectron Spectroscopy (XPS) analyses of used Sequence VE engine parts from highash fully formulated lubricants are shown and the relationship of ECR film formation to fired-engine test performance is discussed.

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.

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.

Soot was recovered from end-of-test (EOT) oils from several different Diesel engines. After resuspending the recovered soots in fresh high dispersancy engine oil, the infrared absorptivities of the soots were determined over a range of frequencies. On the basis of a statistical analysis of the data, recommended 1870 cm-1 absorptivities for soots from various engine tests are: GM 6.2 L, Mack T-8, Cummins L-10 HST, 59.0±0.5; GM 6.2 L, Mack T-8, Caterpillar 3176, 0.02% sulfur fuel, 58.2±0.4; Caterpillar 3176, 0.02% sulfur fuel and 0.2% sulfur fuel, 56.7±0.3; Caterpillar 3116, 53.3±0.4 and OM 602A, 47.8±0.2. In all cases, the units for the absorptivity are cm2/centigram. Over the range of 3800 cm-1 to 1870 cm-1, the dependence of absorptivity on frequency was linear for all the soots. Use of these absorptivities to determine soot concentrations in used engine oils is discussed. Of particular concern are the procedures required to obtain reproducible results.

“Oil thickening” due to soot has long been recognized as a potential problem in diesel engine lubrication. Soot-related viscosity increase in used crankcase oils is remarkable in that relatively small concentrations of soot produce large viscosity increases. Classical studies of suspensions of rigid nonagglomerating spheres in liquids suggest that the viscosity increase produced by 6% (by weight) soot in an oil should be less than 10%. In fact, the viscosity increase in such a mixture may be as much as several hundred percent. This discrepancy implies that the effective volume occupied by soot particles suspended in oil is very large. Past theoretical and experimental work on the rheology of particle suspensions provides a method of quantitatively determining the effective volumes (“voluminosities”) of soots in oil suspensions. Three different used oils were characterized by controlled shear rate rheometry.