Maintenance managers are well aware that motor oil is the lifeblood of the engines that power heavy-duty trucks down the road.

That’s why they seek to ensure they’re using the lubricants that deliver the best longevity and durability performance given the application and duty cycle of their trucks.

Yet, according to one major lube supplier, lubricant decisions that may have consistently paid off for some time may now need to be reconsidered—especially by certain fleets. 

There are two reasons for this concern, Jim Gambill, North America Commercial & Industrial brands manager for Chevron told Fleet Owner.

First off-- and of immediate concern-- are the significant operational changes under way at some freight-hauling fleets that are “leading to many trucks now being run very differently than in recent years,” said Gambill.

Secondly, albeit a few years off, there’s the potential impact on the real-world capabilities of engine lubes formulated per  the next API oil-service category—or oil categories—  yet to be released. Work on this gargantuan task is ongoing, via the development of what’s termed Proposed Category 11 (PC-11) by lubricant formulators and other engineers with supplier stakeholders.

Back to the present: “Chevron is seeing an increase in what amounts to more severe-duty operation of trucks-- due to a dramatic shift in freight patterns,” Gambill stated. “And we concerned fleets may not be considering what this might mean to their maintenance practices.”

He pointed out that certain fleets are now essentially running more “multi-service” trucks-- the same vehicle will operate over the road at night and then make deliveries in cities and towns during the day.

Gambill said the duty cycle of these dual-use trucks becomes more severe vs. what it was when a given truck only operated on the highway. That’s because, when they’re working locally, their engines are shut down much more often, either manually or via automatic shutdown systems aimed at curbing idling.

The upshot is “the oil is getting heated up more and often,” explained Gambill. “And over time, every increase in average temperature of 20 degrees can cut the oil’s lifespan by 50%."

"Pushing up average oil temperature over time does affect the job the oil must perform," he added. And he noted this caveat: Temperature-increase data will vary by engine size and other factors.

“It used to be with a Class 8 tractor that the driver would turn on the engine on Monday and not turn it off again until Friday,” he noted. “The same truck now getting turned on and off and ‘cold-killed’ so much when operating locally is impacting oil longevity. In addition, these trucks are now engaged in more stop-and-go traffic and that cuts their fuel efficiency.

While “all of this has been documented,” Gambill contended that “whether or not these negative impacts are being addressed by maintenance practices is the question that should concern fleets.”

He advised that fleets now running such double-duty tractors should explore whether their lube-related practices are still up to snuff by first looking closely at oil-analysis data.

“Don’t let reviewing that information become routine,” Gambill noted, “and pay special attention to the oil’s rate of oxidation and its viscosity performance.

“Once the fleet has reviewed their data,” he continued, “we recommend consulting with the fleet’s oil supplier, engine builder and its own maintenance staff to determine the best approach to attaining the lowest total cost for lubrication protection, including drain intervals,  on such trucks.”

Gambill added that after looking into what may be happening with engine oil in a multi-use operation, the fleet “may consider adopting a ‘premium’ motor oil” as those are formulated specifically  “to better resist oxidation as well as to help protect the engine’s fuel efficiency potential and to maximize drain intervals.”