Oil Drains & The '07 Engines

There's good news on CJ-4 oils for fleets that want to extend drain intervals.

Deborah Lockridge • Senior Editor

When we talked with oil companies a year ago about the new oils needed for the 2007 engines, there were still a number of unanswered questions. One question was whether oils meeting the new CJ-4 category defined by API would work well for fleets that wanted to extend their oil drain intervals out beyond the engine manufacturers' recommendations.

With another year of tests under their belt, however, oil experts are cautiously optimistic that the new oils, especially the premium brands, could work very well in extended drain interval programs – perhaps even better.

Better Oils

The number of 2007 engines on the road is still too small to be able to offer meaningful statistics on how they will perform in extended-drain scenarios. Nevertheless, the oil suppliers we talked to are confident that many of the new oils will do well in this area.

Steven Goodier, technology manager for BP Castrol, points out that CJ-4 technology, although it offers higher performance than previous categories, is not designed to deliver extended oil drains.

"However, as the change in formulation is so radical, it has been possible to further boost the formula to offer extended drain capabilities," he says, noting that the new CJ-4 formula of Castrol Hypuron, which has higher TBN levels and a semi-synthetic base, can offer up to two times OEM drains.

"We have some product in service, but we don't have anyone pushing the envelop of extended drains," says Mark Betner, heavy-duty lubricant manager for Citgo Lubricants. "We're just now getting the CJ-4s rolling to where you would get a good fleet look. When you think about extended drains, you've got to look at three to four drain intervals to get a good picture, and that's a nine- to 12-month evaluation period."

However, he notes, "if you do a comparison based on development test engine results, we clearly see a performance advantage in CJ-4 compared to CI-4 Plus. I would say there is clearly a potential for optimizing drain intervals in some well-managed fleets."

John Shepard, commercial on-highway marketing specialist for Chevron Products Co., similarly notes that Chevron's testing has found equal and better performance with its Delo 400 LE CJ-4 oil when used with ultra low sulfur diesel in regard to extended drains and engine durability. That's in comparison with the Delo CI-4 Plus version.

"From what we've seen so far, Mobil Delvac customers can expect the same extended performance they've seen with CI-4 Plus oils," says Brianne Wissel, products technical adviser for ExxonMobil's commercial vehicle lubricants business. "We've seen some customers that have extended their drains out to 40,000 miles, which is even better than they had with the CI-4 Plus product."

The TBN Question

One of the key changes to the CJ-4 oils that caused some concern about extended drains is that they typically have a little lower TBN (Total Base Number) – a measurement of the oil's ability to neutralize acids formed by combustion.

The lower TBN came about because the new oils were designed with lower levels of ash, sulfur and phosphorus. These elements were cut because they could plug the diesel particulate filter – but they were also components of the additives traditionally used to combat acid.

However, the new oils don't need as much TBN because diesel fuel for on-highway use now contains much lower levels of acid-producing sulfur. Testing has shown that with the ultra low sulfur diesel, the rate of TBN depletion is less. "Less sulfur means less acid formed, which means less acid needs to be neutralized," says Dan Arcy, product marketing manager for Shell Lubricants.

In the past, explains Reginald Dias, director of commercial products for ConocoPhillips Lubricants, each time the oil category changed, TBN numbers went up. "This is the first time we've had a lubricant with a lower TBN (that) is of better quality," he says. "So it's a change of paradigm in our industry. In communications with our customers, we stress that lower TBN doesn't mean the quality is inferior."

As Betner explains, even though oil companies had to cut back on things that produced ash and other byproducts that could prematurely clog the DPF, they put other additives into the oils to make them more robust.

"We were able to cut back on some things that didn't necessarily contribute to overall engine performance – things that were in there because we had high-sulfur fuel."

Betner compares it to your doctor prescribing a medication to address a certain medical condition, and that medication having side effects. "So basically some of those things we put in the oils did handle the high-sulfur fuel, but did not, in the long run, lead to the best performance overall for the engine. Now we are able to use technology that I think is better."

What Used Oil Tells You

As always, a used-oil analysis program is a must if you're going to safely extend your oil drain intervals beyond the standard engine maker's recommendations. But if you're switching to CJ-4 oils, you'll need to make sure you and your oil analysis lab understand how the new oils are different chemically.

"The CJ-4 oils are quite different from the CI-4 Plus in terms of chemical composition," Dias says. "That means the typical CJ-4 lubricant will have a very different 'fingerprint.' "

Because of this, it's important when you switch to CJ-4 oils to start with a new baseline with your used oil analysis. Look at trends as they relate to that baseline. Don't compare oil analysis from your new CJ-4 oils to the results from the old CI-4-Plus oils.

"We recommend users make sure their oil analysis lab has a reference sample available – a sample of the fresh CJ-4 product that they're using – so they can get the best analysis," says ExxonMobil's Wissel.

For example, in Shell Rotella T, there was a change in the amount of calcium and the addition of boron into the oil, Arcy says. "If the oil analysis lab knows about it, they're going to know what to look for."

It's still important to pay attention to the TBN trends in your used oil sampling if you want to extend drain intervals. Even though sulfur levels have dropped, BP's Goodier notes, EGR has increased in the 2007 engines – and EGR tends to put more acid into the oil.

Some oil companies say you should be looking at TAN (Total Acid Number) just as much as TBN levels. "I think (as an industry) we've put way too much emphasis on TBN," says Betner. "We (at Citgo) tell people to look at TAN and lead. TAN is a measure of the buildup of acid, and also tells you to some degree how much breakdown, how much oxidation is occurring. We also know as acid builds up, it impacts bearing material in the engine, which is where the lead is. If lead is high and TAN is high, you may have a real corrosion problem."

In fact, Chevron's Shepard says close monitoring of lead may be even better than TBN or TAN. "With CJ-4, a more sensitive indicator that an oil has given its all can be lead levels, and this can enable hundreds and thousands of additional miles service from an oil."

Also because of the increased EGR in the new engines, you may need to pay more attention to soot levels and increased viscosity that may result from too much soot in the oil.

"You're still going to want to make sure that the program you choose looks at soot," Arcy says. "In some applications, soot may be more of a limiting factor than anything else. That's not going to change with the type of oil."

You also may want to keep in mind that if you're using CI-4-Plus oils, but a driver tops off with CJ-4 oil on the road, it could change the oil analysis results slightly. For instance, Arcy says, if you use the CJ-4 version of Shell's Rimula oil to top off an engine containing the CI-4 Plus version of Rimula, the oil analysis would suddenly show magnesium and moly. If you had 20 percent of the new oil in an engine previously filled only with the CI-4 version, it might be enough moly to set off an erroneous flag on your report indicating possible ring wear.

Betner also says when you switch from CI-4 Plus to CJ-4, you may see some anomalies in your first oil analysis reports. This can also happen when switching brands within the same API category, he says.

"For instance, some engines have an oil cooler where, when you change formulations, the new formulation lifts off a film that has formed on it and makes it look like you have high copper levels. But over a matter of time, that copper dissipates." That's why it's important to watch trends – a single oil analysis report could be misleading.

Nearly everyone we talked to stressed that extended oil drain intervals are not for everyone. The ability to extend drains depends on a large number of factors, including engine designs, the quality of a fleet's maintenance program, types of service and the oil used. If you want to extend oil drains, make sure you've got a good used-oil analysis program in place and work closely with your engine manufacturer and lubricant supplier.