Fleetowner 6703 Enginetest1e

Maintenance Bay: Test process

Sept. 6, 2016

Manager: Tim Proctor, technical leader of heavy-duty engineering

Company: Cummins Inc.

Operation: A fleet of 10 in-house engineering trucks and 40 customer demonstration trucks


How far can one safely extend heavy truck engine oil drain intervals? That’s a question fleets have been asking for some time. And while using an oil analysis program helps determine whether the lubricant still retains its protective properties, it takes a long time to determine just how far the oil can go.

As the technical leader behind the development of the 2017-compliant line of new Cummins X15 and X12 truck engines, Tim Proctor’s the guy tasked with determining how far the OEM is willing to extend oil drain intervals for its new products.

Over the last four years, Proctor helped guide some 9 million mi. worth of field testing for Cummins’ new engines using 10 engineering trucks operated by his staff and 40 “demonstration” vehicles loaned out to customers of Cummins.

“We look to establish what we call ‘corner tests,’ as in testing our engines in applications at the ‘extreme corners’ of the industry” such as logging or heavy haul and also in extreme cold and heat. “We know if we can meet the needs of the corners, we can easily meet the needs of the average fleet,” Proctor explains.


To speed up the data-gathering process for extending oil drains, Proctor put what’s known as “degraded oil” into the prototype X15 and X12 engines. Typically, such oil would already have experienced between 50,000 and 80,000 mi. of use, thus placing it  outside the oil change window.

“Then we’d push that degraded oil as far out as possible,” Proctor notes, adding that a close examination of the chemical trend line of the oil through extensive oil sampling was conducted.

Such degraded oil testing helped Cummins make some determinations.The first revolved around a change in materials for lubricated engine components such as bearings. Degraded oil typically harbors higher levels of acids, which cause pitting in the surface of the bearings. This means they operate less efficiently and thus lower fuel economy. Changes to the material used to make bearings helped reduce this issue, Proctor says.

Second, oil analysis not only proved that Cummins could establish a 50,000-mi. drain interval for its X15 and X12 engines but that testing programs were critical.

As a result, Cummins is now offering OilGuard, its own in-house oil analysis service. With this option, fleets purchasing X15 and X12 engines can safely extend drain intervals out to as much as 80,000 mi., depending on duty cycle and the type of lubricant used.

And the third and final piece of the oil drain extension puzzle centered on engine fuel economy. Proctor’s engineering team determined that, based on 9 million mi. of field tests, trucks getting at least 6.5 mpg were the ideal candidates for extended drains.

“Fuel economy is the key because the less fuel burned within the engine means there is less buildup of contaminants, et cetera, that can affect the life of the engine oil,” he explains.

About the Author

Sean Kilcarr | Editor in Chief

Sean previously reported and commented on trends affecting the many different strata of the trucking industry. Also be sure to visit Sean's blog Trucks at Work where he offers analysis on a variety of different topics inside the trucking industry.

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