Because the decision to schedule oil changes, either interval-based or on-condition, must take into consideration a number of factors, a worksheet or scorecard has been developed to guide the process. This is referred to as the Condition-Based Oil Change Scorecard (Figure 1).
The Scorecard deploys a scoring system that enables the user to simply complete a series of nine questions, which when totaled, give a composite score. A composite score of 100 or more suggests that the machine is a good candidate to run oil changes based on- condition. A score greater than 200 gives near certainty to the decision. Following is a discussion of the rationale of the nine scoring elements:
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1. Lubricant Volume: If time and effort must be exerted to extend oil drains using a condition-based strategy, the total amount of lubricant involved needs to be factored in. If the extended drain saves little fluid (small oil compartment) the cost may not be justified, even if the benefits were extended threefold. Read on, because there are other cost/benefit factors to consider.
2. Makeup Rate: Lubricant compartments that undergo high makeup rates due to leakage, oil burn or other causes of fluid loss may never need to be changed. The new makeup fluid not only introduces more additive to the system but also dilutes the concentration of contamination (water, dirt, etc.), acids and other degradation precursors.
3. Lubricant Cost: The more expensive a lubricant, the greater the motivation to save the oil from a premature drain. Many specialty and synthetic fluids can cost 10 times more than their less expensive counterparts. Because one of the driving factors for purchasing specialty lubricants is long life, a more precise decision in timing the oil change is justified in most cases.
Reclaiming used oils is also a consideration here. The cost of reclaiming and reconstructing additives, when needed, is in essence an oil change but at a lower cost (potentially) than the physical replacement of the oil. A partial drain (bleed and feed) is yet another consideration.
4. Nonlubricant Costs: There are many cost factors in performing an oil change that go beyond the cost of the oil itself. These need to be weighed in terms of the benefit coming from more precisely selected lube change intervals using the on-condition strategy.
For typical examples of such costs, refer to the above list in the article “Hidden Costs of an Oil Change.”2
5. Machine Accessibility: Many machine lubricant compartments, including fill and drain ports, are not accessible for routine maintenance. In such cases, the need for access must be planned well in advance, keeping the frequency to a minimum. The use of oil analysis to forecast oil change needs to avoid unnecessary change-outs could be of considerable practical benefit.
6. OEM Recommended Change Interval: Many OEMs have precise guidelines for when lubricants should be serviced. Others offer minimal advice. Because machine operating conditions (loads, speeds, temperatures, etc.) vary considerably, the service manual
recommendation will often be on the far side of conservatism.
This can lead to repeated premature interval-based scheduled changes. This part of the scorecard favors condition-based oil changes when the OEM advises longer change-out intervals. In such case, there is a more manageable timeline to monitor the oil and plan lubrication work orders.
7. Oil Analysis Availability: While oil analysis is highly accessible for most organizations, there are many instances when machine lubes cannot be sampled or convenient laboratory analysis is not available. This may be due to geography (remote locations of equipment), manpower issues or a host of other reasons. Clearly, the more frequently oil analysis can be performed, the more effective and dependable the on-condition oil change strategy can be. On-site oil analysis offers clear benefits here but the cost and manpower to provide the service on-site can, in cases, be a significant offset.
8. Penalty of Failure: For machines that present high safety risk or downtime cost in the instance of operational failure, it may be prohibitive to switch entirely from interval-based programs. In these cases, the benefits don’t outweigh the risks. Often, when a high degree of reliability is desired, the best plan is a combination of condition-based and interval-based - the oil is changed whenever either first occurs. Because oils can occasionally experience premature failure or a wrong lubricant is introduced, such a combined strategy can make the best business sense.
9. Quality of Filtration: Proactive maintenance is what gives lubricants longer and more reliable service life. When lubricants are routinely kept clean, dry additives last longer and lubricated surfaces are less challenged (corrosion, abrasion, etc.). High quality contamination control improves the opportunity to extend and plan drain intervals on-condition. In contrast, lubricants loaded with contaminants due to high ingression or poor filtration will often need to be changed to avoid distress to surfaces, regardless of whether other fluid properties have degraded. In such cases, the oil change becomes the default maintenance procedure for eradicating dirt and water from the machine - not exactly ideal, but often the only practical plan.
Also worth consideration is the concern that new lubricants may not be much cleaner than the lubricant being replaced.
Moreover, the cost of filtration is a factor as well.
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• Seek 50% reduction each year until a consumption ratio of less than 0.1 is achieved. Varies by industry and age of machine.
Annual Oil Purchases Machine Charge Volume Consumption Ratio =
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