From "Lubrication Fundamentals"

Solid particles of any kind that are trapped between the rolling elements and raceways are the most frequent cause of shortened bearing life. Consequently, dirt should be kept out of bearings as much as possible, and lubricants should be changed before oxidation has progressed to the point where deposits begin to form. The use of oxidation-inhibited lubricants can greatly extend the period of time that lubricants may be left in service without excessive oxidation.

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QUESTION: When an SAE 20 is blended with an SAE 40, will the resulted viscosity be closer to SAE 30 or SAE 60?

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"What is the meaning of "the life cycle cost of oil" and how is it calculated?"

Sometimes a higher performance product costs less than a commodity-type product, even though the price is higher. To gauge whether this will be the case we should look at the product life cycle cost, rather than the purchase price.

The life cycle cost of oil is effectively the total long term use cost for a given product from oil change to oil change. There are a variety of indirect, but none-the-less valid, costs and time commitments that factor into an oil change, including the following:

1. Oil specification.

2. Oil purchase, including: purchase document generation and sending purchase document.

3. Cost of the oil itself.

4. Oil receipt and storage, including: tracking of shipment paperwork to affirm receipt and re-work for errors and omissions.

5. Invoice receipt, approval and payment (this item alone can add a lot to the real cost of plant lubrication).

6. Oil transfer to the user or the asset.

7. Oil disposal cost, if any.

8. Cost of labor associated with the oil change.

9. Cost of other materials associated with an oil change.

10. Cost of monitoring the new oil for the life of the oil.

11. Cost of degradation effect, including loss of oil strength, loss of filterability, loss of cleanliness, corrosion and corruption of mechanical surfaces.

12. Cost of machine downtime if there is any associated with the oil change.

There may be other costs that you could identify for your specific organization.

If you estimate each actual incremental cost or time requirement, apply a normalized labor rate for the time, and then add the various costs together, you could fairly accurately guess the total life cycle cost of an oil change at your facility. It is higher than you might expect.

While all of these items do not show up in the obvious as a line-item in the maintenance budget report (which is generally limited to the cost of the purchase itself, and is measure by cost per pound or cost per gallon), the costs are nonetheless absorbed by the organization and add to the total cost per item manufactured.

Mike Johnson, Noria Corporation

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