Crunching numbers

Oil analysis can measure the level of various metals and qualities such as acidity and viscocity – which may increase or decrease, depending upon operating conditions or particular engine problems.

It’s a brave new world under your hood: a new, low-sulfur fuel, a new engine oil that’s much more potent in nearly all respects, and new engines – all with diesel particulate filters and most with higher rates of exhaust gas recirculation. Even Caterpillar’s ACERT technology now recirculates some exhaust. As a result, expect major changes in oil analysis results.ACERT technology now recirculates some exhaust. As a result, expect major changes in oil analysis results.

“The signature of the oil will change,” says Dan Arcy, technical marketing manager for Shell Lubricants. “This means that the standards, in terms of what you’re looking for, are different.”

Consequently, “You cannot interpret analysis results on your own,” says Steve Goodier, Americas technology manager at BP Castrol. “You need to talk to your supplier and get the approved limits. Good advice will be included if you subscribe to a regular analysis program with a responsible lab.”

Especially important is telling your lab exactly what oil you are using. That includes prior oil if you’ve switched to the new standard, CJ-4, as well as any stopgap oil you’ve used in a pinch.

Responsible testing labs will confer with oil makers to find out what the basic constituents of the oil are and what the various limits should be. Without that knowledge, any interpretation of the report could be meaningless.

CJ-4 normally has slightly less acid protection, as measured by total base number. Mark Betner, heavy duty lubricants manager at Citgo Petroleum Corp., estimates TBN dropping from the 11-to-13 range to 10 for CJ-4.

“Make sure your TBN is not getting too low because this would cause corrosion wear in the engine,” says Goodier. “Modern engines have increased EGR, which can increase the acidity of the lube oil.”

Chevron did three tests of CJ-4 on pre-2007 engines running on low-sulfur diesel, says Jim McGeehan, global manager of diesel engine oil technology. “The positive thing that came out of this is that CJ-4 is fully backward compatible and good for pre-2007 engines, based on used oil analysis, looking at iron, lead, and chromium metals,” he says. In one fleet running lightly loaded vehicles, a test of extended intervals showed the oil was still good at 60,000 miles, with no difference between CJ-4 and CI-4 Plus performance.

One factor that may help is that low-sulfur diesel typically contains only 375 parts per million sulfur and normally does not reach the 500 ppm maximum, McGeehan says.

McGeehan also had good news based on oil analysis from a few fleets running ultra-low-sulfur diesel: “Just reducing the sulfur from 375 ppm down to 10 produced a 35 percent reduction in iron wear.” Technicians found reduced levels of iron, then removed and measured the cylinder liners to confirm the wear reduction.

“When you reduce the fuel sulfur, you reduce the amount of acid formed in the cylinder,” says McGeehan. “This is an effect some fleets may see, depending upon the type of service.”

Shell has noticed as much as a 38 percent reduction in engine wear for some fleets running CJ-4. Less metal in the oil could prove a bonanza, and not just because engines may run longer before overhaul.

“Some engine manufacturers have a 150 ppm limit on iron wear in the oil, and want you to change at that point,” says Arcy. “If you are already a good candidate for extending your change interval, and your iron wear stays under the allowable maximum, you may be able to extend. This kind of shift in analysis results is always a good opportunity to re-evaluate your interval.”

Arcy sees another potential gain: “We are looking at a possible step change in performance with ULSD. TBN drops off at a slower rate, and this, too, may allow you to extend. Stay tuned.”

McGeehan agrees that it’s too early to confirm any increased change interval potential. “It takes time to build up analysis data. We need a few oil drains. Fortunately, we have not seen any issues so far.”

However, McGeehan notes concern about “a 60 percent increase or even double the EGR rates. Even with ACERT, we have a form of EGR, clean gas induction. Of course, 15 ppm sulfur fuel is a positive.”

“We can’t yet do a comparison between 2006 and 2007,” says Arcy. “Both the oils used and the engines have changed.” Further, Shell’s agreements with the engine manufacturers prohibit specific comment until there has been more time to gather and evaluate the data. Arcy is optimistic about the possibilities, however, mentioning CJ-4’s “better wear protection, deposit control, oxidation control and the lower sulfur level.”

“The new oils were licensed only in October,” says Citgo’s Betner. “You need at least three or four oil samples to begin to see a trend change.”

He’s also optimistic, though. “If you use ULSD and CJ-4 in a 2002 engine, you’ll see nothing but advantages. These oils have better soot control and viscosity control, so they stay in grade better. A premium CJ-4 actually has twice the soot-carrying ability of earlier oils.”
Betner also believes the lower ash limits will be good for the engine. Oil engineers wanted to find ways to lower ash limits years ago, he says.

In 2007 engines, however, “with higher soot-loading and operating temperature, there could be indications that some oils will deteriorate faster, especially in severe service,” Betner says. “One variable will be what quality level oil you are using. Ask your supplier what the advantages would be to using a better oil,” since almost every refiner makes “a good, a better and a best oil.”

ExxonMobil’s Doug Pond, commercial vehicle lubricant products adviser, says, “We have one of the highest TBN levels at 10.5.” But, because CJ-4 oils must have less ash, 10.5 is lower than levels of earlier oils from his company. With better fuels and oils, there is much less need for this form of protection.

ExxonMobil uses a proprietary form of TBN additive that provides more protection with less ash – hence the ability to have a slightly higher level of protection than some others. They also have increased the stability of their base stocks through better refining, which reduces the TBN requirement.

Another reassurance during the transition to new technology is the developmental work that went into the new engines. The manufacturers made substantial improvements so their iron would easily take the stress. While caution always is the rule, the end result may be positive.

Oil makers recommend doing oil analysis even if you’re following conservative, factory-recommended change intervals. Analysis “can show any lube deficiencies and let you know if fuel or coolant is getting into the oil,” says BP Castrol’s Goodier. “Water or dirt are disastrous, and can be a problem even in a new engine. It’s a sensible way to protect your investment.”

“Coolant leaks or fuel dilution cause serious problems,” McGeehan says. “Coolant is corrosive, and fuel reduces the viscosity of the oil.”

The basics of using analysis to extend changes remain the same. The operations that are good candidates must have low idle time and be getting good fuel economy.

CJ-4 costs about 10 percent more than CI-4 Plus, but when used with the new fuel, which also costs a little more, it will be better for your engine.

Take a careful look at it through analysis, and make sure your results are right by knowing what to expect and getting good advice. Finally, use that knowledge to evaluate the lube’s performance and your change interval.

Taking these steps could well allow you to more than recoup the extra cost of the oil and fuel by saving money on oil changes and engine overhauls.

Since the primary value in oil analysis is checking trends, Shell Lubricants’ Dan Arcy recommends doing all you can to keep your oil samples uniform.

“Make sure the engine is always warm,” Arcy says. “Don’t pull the sample out through the dipstick one time, and out of the draining stream the next.”

If pulling it from the stream of oil headed for the collection pan, make sure to take it at the same time each test.

“You have to get as many of the variables out of the picture as you can,” Arcy says.

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