Oil Bay: Analyze This

The trucking industry’s efforts to comply with stricter vehicle emissions regulations have not been kind to engine oils. From the moment that exhaust gas recirculation (EGR) systems were first introduced, engine lubricants have been exposed to everything from heavier soot loads to higher ignition temperatures.

So it should be of little surprise that service providers should be urging their customers running 2002 emissions-compliant engines toward regular oil analysis.

“Five years ago, people primarily did an oil analysis to look at wear metals and to look at coolant contamination, dirt, things like that,” says Jason Papacek, data analysis manager for Polaris Laboratories. “Today – along with that – they’re more interested in fuel dilution, soot and the TBN [Total Base Number].”

Engine oils obviously deserve some added attention. Before the introduction of EGR, Papacek rarely saw soot loads that reached beyond 2 or 3 percent. In contrast, today’s reports often show levels that approach 5 percent.

“There’s a very clear correlation between the soot level and the amount of engine wear,” he adds. In an analysis, chromium levels can begin to indicate damage to piston rings. There also can be worrisome readings of iron or aluminum, depending on the metallurgy of the engine block and liner.

Luckily, oil formulas have evolved to address many EGR-related challenges, notes Walt Silveira, North American technical manager for Shell Lubricants. For instance, the CI-4 Plus formulas were certainly better able to handle higher heat, combat the resulting oxidation and better disperse soot than previous oil formulas.

ExxonMobil’s Lilo Hurtado, a commercial vehicle lubricant application engineer, reports that soot loads leveled off and even dropped in engines built since 2005. Refined calibrations and hardware upgrades may share the credit, he suggests.

For customers wishing to extend drain intervals, this has been good news.

“Some fleets changed their drain intervals, but not really that much,” Papacek says, referring to the difference between pre-EGR engines and the equipment that is available today. “Maybe a 5 to 8 percent decrease.”

Edward Sikorski, manager of technical services at Agat Laboratories, counters that some fleets may be placing too much confidence in the improved oils. “It used to be that anything over 1 percent was flagged as ‘critical’,” he says, referring to the alarm limits that draw attention to soot loads. “Now they’re changing the limit to 5 percent.”

That isn’t the only increase catching his attention.

“The worst thing is really high copper,” he adds.

The cause of a spike in copper might be a matter of debate. Papacek suggests the higher readings usually are linked to a switch between oil formulas. In these cases, the copper can be traced to a thin varnish that accumulates on the copper tubing that runs through the oil cooler. “It [the addition of new oil] seems to clean off that varnish. Once the new oil forms its own varnish layer that will start to taper off and eventually subside.”

Of course, maintenance teams still need to know about the metallurgy in the engines that they use, adds Hurtado. For instance, Cummins makes its oil coolers out of aluminum so any copper in the oil from these power plants is coming from another source.

It is just one example of why you need to pay close attention to the entire story of an oil analysis. Just consider an increase in potassium, which traditionally indicated the presence of coolant. When that reading is coupled with an increase in aluminum and a low level of sodium during an engine’s break-in period, the potassium may be from residual brazing flux in the charge air cooler – and the levels eventually will return to normal. But after the same engine runs 350,000 miles, the higher levels of aluminum and potassium, when coupled with a spike in soot loads, can suggest a serious problem with the emission-cleaning components.

Other problems with an EGR cooler can manifest themselves as increases in chromium and nickel, Hurtado says. “If you’re not really watching it, you may overlook it.” But again, nothing can be taken for granted. The chromium levels also can be linked to the chrome-faced rings that still are used in some engine designs.

Beyond the focus on wear metals, professor Robert Kauffman of the University of Dayton Research Institute says today’s fleets should pay particular attention to antioxidant levels.

“Once the antioxidants deplete, oil degradation will occur,” he explains, noting that this can be a significant problem because of the higher operating temperatures in the NOx-reducing engines.

In contrast, Kauffman says there is little value in a viscosity reading that will spot fuel or water in the oil because once that problem is detected, the damage already has been done.

The switch from CI-4 oils to the new CJ-4 formulas present another sort of challenge for analysis programs.

When CI-4 oils first were introduced, technicians began to pay more attention to the TBN because the oil formulas had to counteract the damaging acids that were generated through the combustion process. But the introduction of ultra-low sulfur diesel fuel now helps ensure the acids are less likely to form. As a result, a CJ-4 oil can feature a lower TBN than the formulas that came before it.

In most cases, Papecek says there will be little cause for concern. “Even though they have a lower starting TBN, the depletion rate is not as fast,” he observes.

Hurtado notes that customers operating vehicles with harsh duty cycles should still watch these levels.

The need to consider a pair of limits is an unusual situation. In the past, every new category of oil simply replaced the formulas that came before it. But today’s marketplace has fleets using a mixture of the oils, and in some cases CJ-4 is used only in the 2007-08 engines that are equipped with DPFs.

Silveira is quick to note that the CI-4 Plus users are missing out on the additional features of CJ-4 that can help an engine of any age, such as improved wear performance and deposit controls. “At what point,” he says, “do they make the decision that they have a large enough mix in their fleet?”

Regardless of the oil that is being used, an oil analysis program is still vital for customers who want to extend drain intervals. For his part, Kauffman has helped to introduce a sensor known as the Intellistick which can offer analysis results through a wireless device. And, of course, a growing number of shops also are adding sample bottles to their list of tools.

Sikorski looks at any analysis program as a form of cheap insurance.

“Oil analyses are not expensive, compared to what the engine is worth,” he says.

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