The break point occurs when one or more oil-analysis trend becomes non-linear. A drain interval set 30 percent shorter than the break point is acceptable.

THE DRAIN STARTS HERE
While some fleet operators have experimented with extended oil-drain intervals, others have pulled in the reins and shortened them as a conservative approach to caring for new, lower-emitting diesel engines.

But how do you home in on an interval that protects your equipment, while saving your fleet from the expense of unnecessarily frequent service? Experts at this summer’s meeting of the Technology & Maintenance Council offered these guidelines to get you started:

While all agreed that used oil analysis is fundamental to establishing a safe interval, Reginald Dias, director, commercial lubricants, ConocoPhillips, notes that many factors affect service oil life, including engine characteristics, operation severity, maintenance practices and oil and fuel quality.

He advised first selecting the right oil, which means one that carries the correct API/SAE service category, meets your engine manufacturer’s specifications and is on the approved products list for that engine. Documentation and proof of performance, he said, should be available from your lubricant supplier.

Next, he continued, have an unused sample of the chosen oil analyzed. The results can be compared to the product’s specifications and used for a baseline. If, for example, you see copper or silicon in subsequent analyses, you’ll know whether it came from engine wear/contamination, or if it was already in the oil’s additive package.

Using the manufacturer’s drain recommendation as an initial guide, he said, you can: use oil analysis to identify trends, monitor the condition of used oil and determine whether it is still usable; establish oil drain intervals for particular engines and service; possibly take advantage of extended drain capability; and diagnose potential engine problems, such as abnormal wear, coolant leaks and fuel dilution.