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4. Due to inconsistency in the sampling frequency and missing samples, graphical trending of the data for each vehicle was found unsuitable. Therefore the test results have been tabulated in appendix D and color coded to indicate events such as exceedances, oil change, missing or erroneous usage information, etc. Each set of test results have been provided with an individual explanation and an overall assessment of the data collected from each vehicle.
5. Based on the limited number of commercial pattern vehicles selected (approximately 0.1% of the fleet) for this phase of the project, there was no benefit in conducting statistical analysis on the test data. The following paragraphs are conclusions derived from the actual test results and observations collected throughout phase I of the project.
6. In general, the load carrying property (viscosity) showed slight degradation with increased usage. Variations in oil formulation (i.e. new oil with lower or higher viscosity) may have generated false alarms.
7. The oil acidity, represented by the Total Acid Number (TAN), which relates to the level of oil oxidation was affected by the presence of moisture and copper (Cu) wear debris. Engines with worn bearings and bushings, for example containing copper (Cu) were more likely to show high TAN than engines with no worn bearings and bushings. Oxidized oil with elevated acidity (TAN) will usually be accompanied with a significant variation in viscosity. Severely oxidized oil can promote the formation of varnishes; insoluble (i.e. sludge) and increase wear metals concentrations due to load carrying capacity losses due to poor viscosity, which can lead to premature oil-wetted component failures. In most instances during this phase, when the oil acidity was high, the viscosity remained within tolerance, which indicated that the oil was not necessarily degraded. This incoherence between the oil acidity and its viscosity could be explained in part by variations in the acidity level of the new oils used. New oils yielded TANs ranging from 0.59 to 5.1. With a maximum acidity limit set at 5 mg KOH/g, new oils with elevated TANs had their useful life significantly reduced. A better evaluation of the oil oxidation could be made by taking into account both, the set limit (i.e. 5 mg KOH/g) and the actual spread between the new and used oil values.
8. No engine component failure was induced by degraded oil during this phase. Using spectrometric oil analysis, a number of worn engine oil-wetted components were found and monitored throughout the project. Suspected coolant leaks were also identified.
10. Deviations from agreed sampling routine could have been a contributing factor for unexplainable variations in wear metal levels observed for some of the engines. An oil sample taken 20-30 minutes after engine shut down will contain less wear metals than a sample taken within 5 minutes of engine shut down, as most wear debris will have settled to the bottom of the sump. The introduction of external contaminants such as dirt and sand is also problematic when sampling through the engine oil fill hole.
11. Based on OLOF Phase I findings, additional data and further information need to be collected in order to demonstrate the feasibility of the oil life extension concept. For this reason, it is recommended that a second phase be carried out with a representative cross section of DND’s commercial vehicle fleet to statistically prove the concept and that vehicles locations and types be selected based on the environment they operate in (i.e. precipitation, humidity, temperature) and their use. Lessons learned from Phase I should help in better sampling protocols, experimental control and interpretation of the data.
9. The commercial Instant Lubricant Test was easy to use, the test patch easy to interpret
and the test provided acceptable results more than 80% of the time.
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