Equipment and Maintenance – September 2003

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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.

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.

If you’re looking to extend your drains, get your engine, oil and filter manufacturers involved, suggested Danny Larkin, commercial vehicle lubricant technical advisor, ExxonMobil. Then, pick a target interval and do extensive testing at 30 percent beyond that target. To get meaningful results, he said, involve 10-25 representative vehicles with clean service records and be sure you have at least three units per vehicle configuration.

The units should be available for frequent oil sampling, he added – every 5,000-10,000 miles – with three samples taken per interval. Testing should last six to twelve months, to take into account variations in weather and fuel quality.

Larkin also provided the following tips for effective oil sampling:

  • Install sampling valves in active oil galleries, in locations that are safe to reach with the engine running.
  • Sample before adding make-up oil.
  • Maintain a log book that includes, for each sample, the unit number, date, vehicle miles, oil miles, filter miles, and whether oil has been added since the last sample.

What you’re looking for in the oil analysis are wear/contamination trends, he concluded. When one or more trend becomes non-linear, that’s your break point, and if your target interval is 30 percent shorter than that, you’re probably OK.

However, Amy Szabo, field test engineer, Lubrizol, cautioned that, when evaluating oil analyses, it’s important to know what’s abnormal for what engine(s). There are condemnation

When reviewing oil analyses, keep in mind that what’s normal for one engine could be disastrous for another. Here, if the OEM limit for lead were 50 parts per million, Engine B (red samples) would be in good shape, while Engine A would be headed for trouble.

limits set by each manufacturer, which dictate the maximum allowable parts-per-million or percentage change in wear metals, contaminants and oil characteristics for its products.

The primary reason is that some engines contain more or less of certain materials – chromium from piston rings or copper from bearings, for example – than others. What’s normal for one engine could be disastrous for another.

Finally, Herman Miller, fleet equipment manager, Shopko Stores, advised that, when trying to extend drain intervals:

  • Work with your oil supplier and get in writing what he will do for you to guarantee success.
  • Test new intervals on your worst duty-cycle vehicles that see high loads, high fuel consumption, high idle time, etc.
  • Be 110 percent sure you don’t miss an oil change.
  • Try not to extend your entire PM program. If PMs are getting stretched out too far, add “dry” PMs between drains to keep vehicles in good shape.
  • Have tight processes in place to monitor results and ensure that your goals are being met.


Ever think about outsourcing maintenance management? Or maybe you just need some extra onsite advice with a stubborn maintenance problem. We know just the guy.

Darry Stuart, Wrentham, Mass., has managed some of the largest private, for-hire and leasing fleets in the country, including Perdue, Cumberland Farms, BFI and United Truck Leasing.

A natural-born troubleshooter, Stuart got his start as an ASE-certified Master Mechanic, and quickly moved into maintenance management. He’s been a member of the Technology & Maintenance Council since 1975, has served on its board of directors and been awarded TMC’s highest honor, the Silver Spark Plug. For his contributions to the industry, he received CCJ’s Career Leadership Award in 1998.

We’re talking 35 years’ experience here, and if you think you could benefit from his expertise, you can reach him at DWS Fleet Management, (508) 384-9021 or

Coolant joint venture.

Bar’s Products, makers of vehicle leak-stop products, and Ondeo Nalco (formerly Nalco Chemical Company), makers of supplemental coolant additives and filters, have formed a joint venture, under which Bar’s Products will be the exclusive supplier of co-branded Bar’s Xtreme Nalcool Heavy Duty Coolant products in the United States and Canada.

The 2003/2004 Class Pays Coupon Book, which offers over $3,000 in savings on parts, accessories and service work, is now available at participating Peterbilt dealerships throughout the United States and Canada.

The 65 coupons include discounts for seats, fifth wheels, brake drums, sleeper mattresses, chrome accessories, PACCAR-branded components and Peterbilt’s TruckCare QuickLube service.

Suggested retail price is $9.95. To locate your nearest dealer, call (800) 4-Peterbilt or consult the online dealer locator at