CJ-4 does such a good job of keeping soot dissolved that a valvetrain inspection shows a noticeable reduction in wear. If you carefully examine parts such as pushrod tips and sockets, and other rocker wear surfaces, you likely will notice much less surface pitting. Where valve clearances need to be tightened to compensate for wear, a smaller adjustment may be needed.
The new CJ-4 oil standard was developed for the significantly greater stresses of 2007 and later engines. CJ-4 oil has to handle more heat without oxidizing or breaking down chemically, keep more soot in suspension without increasing viscosity, and do a better job than ever of controlling deposits, sludge and wear. Moreover, the qualification process was made much more detailed and difficult.
“There’s higher quality here, and the tests are more severe,” says Jim McGeehan, Chevron’s global manager of diesel engine oil technology and head of the industry committee that developed the standard. The oil controls acid, disperses soot and withstands wear much better than the previous standard, McGeehan says.
That’s true even for pre-2007 engines. For most owner-operators, a little more spent on CJ-4 could mean significant cost reduction by improving reliability and lengthening engine life. CJ-4 costs about 5 percent to 15 percent more than CI-4 Plus, say oil company representatives, though retail prices can vary substantially.
The main incentive to develop the new standard was the increase in recirculated exhaust in the new engines, necessitated by the latest emissions mandate from the U.S. Environmental Protection Agency. Most 2007 engines need to ingest just as much air as in the past to minimize soot, along with much more exhaust to dampen nitrogen oxide, which aggravates problems such as ozone, acid rain and asthma.
In the engine, this means higher intake and cylinder pressure, more heat and more recirculated exhaust and acid.
Even Caterpillar’s ACERT engines, which meet the EPA’s 2007 challenge with a unique design, allow some exhaust to re-enter the cylinder. While that exhaust carries less soot, having passed through the diesel particulate filter, and less heat, having gone through the charge air cooler, ACERT seems to complete the burn later than other designs. Oils used in Caterpillar engines therefore have particular piston deposit requirements and need to pass Caterpillar ECF-3 standards in addition to CJ-4. Each of the other manufacturers has its own standard.
CJ-4 is a lot better in every area but one: acid neutralization. You can blame the DPF for that. All the soot the DPF catches will be burned off as it accumulates, but that’s not the case for the sulfated ash put into the exhaust stream by the oil, not even when the temperature is increased during active regeneration.
To minimize DPF clogging and to make cleanings as infrequent as possible, CJ-4 oil must contain less ash. But most of the total base number additives that neutralize acid also generate ash. CJ-4 therefore generally has a lower TBN than the previous oil category, CI-4 Plus.
That should not be of consequence because the new 2007 oils and engines were developed as a system with the new 2007 diesel fuel. Much of the acid in the engine comes from sulfur in the fuel, and the new pump standard, ultra-low-sulfur diesel, has 97 percent less sulfur than before. This should more than compensate for the small reduction in acid-fighting agents. “ULSD clearly means less acid in the cylinder,” McGeehan says.
But there’s another balancing factor as well. “Oil itself forms oxidation products, and they are acidic,” says Walt Silveira, U.S. technical manager at Shell. “CJ-4 is oxidation resistant. It’s a much stronger oil as far as oxidation goes.”
The amount of acid the oil has to fight therefore is much lower than before, and early results show CJ-4 running with ULSD retains TBN protection better than CI-4 Plus running with last year’s diesel. What counts is not how much TBN you start out with, but how many miles the protection will last.
There is not much evidence yet for exactly how well this oil will perform in 2007 engines because not that many 2007s are out there, even among large fleets.
“Due to a large pre-buy toward the end of last year, the penetration of the 2007 model low-emissions engines has been very slow,” says Reginald Dias, director of commercial lubricants at Conoco-Phillips.
Engine makers still were building 2006 engines well into 2007, says Stede Granger, OEM technical services manager at Shell. “The model year of the engine is determined by when the crank goes into the block, not by when it’s completed,” Granger says.
Even in-service 2007 engines may not have CJ-4 in their crankcases, McGeehan says. Though Chevron, for example, has switched its Delo 400 and Ursa Premium TDX gallon and pail-size containers exclusively to CJ-4, CI-4 Plus still is available in bulk.
Fleets that run thousands of trucks “do the calculation and decide they don’t need to spend the extra pennies a gallon for CJ-4 with so few engines that have DPFs,” McGeehan says. “They just use CI-4 Plus across the board and clean the DPF more often.”
Cummins and Detroit Diesel specifically allow this, but Caterpillar doesn’t.
As head of the committee that developed the standard, McGeehan has seen reams of data, and he believes the oil so far is working as designed in 2007 engines. “We’re seeing excellent performance and low wear metals,” he says.
Other manufacturers concur. Trucks with 2007 engines in line-haul service can continue 30,000-mile oil changes when running CJ-4, Granger says. Mobil Delvac 1300 Super “will protect 2007 engines run on either ULSD or LSD,” says ExxonMobil’s Brianne Wissel, product technical adviser for commercial lubes.
Engine makers have reduced oil consumption, allowing long-haul fleets to run 400,000 to 500,000 miles before cleaning the DPF, but trucks running in congestion still can use the help of CJ-4 oil, McGeehan says.
“The best condition for oil consumption in diesel engines is under power, when there is cylinder pressure to force the rings into the liner,” McGeehan says. “At an idle, there’s not much pressure, so the rings don’t work as well.”
CJ-4 is certified to be backward compatible with CI-4 Plus. Even with its reduced TBN, using CJ-4 would not likely cause a significant problem unless running an extended change interval – in which case oil analysis clearly would indicate when its time was up.
Those running both on and off road with the increasingly hard to find (but cheaper) low-sulfur diesel, as opposed to ULSD, would be wise to follow the engine manufacturer’s oil change recommendations, or to buy a premium oil guaranteed to provide more than sufficient acid prevention.
BUYING TIME: EXTENDED DRAINS STILL A QUESTION
With 2007 engines far from a teardown, it’s not yet certain that the slightly more expensive CJ-4 oil merits extended service intervals. All the experts can do is examine oil analyses with a magnifying glass.
“So far, we’re pleased to see we can maintain the same drain with the drop in ash,” says Chevron’s Jim McGeehan. “But we don’t have sufficient data under our belt to pull the change interval out yet.”
Today’s diesels take at least 100,000 miles to break in, and few 2007 engines have a lot of miles.
McGeehan is optimistic, though. “We’re seeing very low wear,” he says. “This corresponds with engine test data gathered earlier. We hope to see longer engine life.”
“Customers already on extended drains can keep that up,” says Brianne Wissel of ExxonMobil. “Proceeding cautiously, you can extend drains to up to 45,000 miles.”
ExxonMobil offers Mobil Delvac Elite, a synthetic blend, and fully synthetic Mobil Delvac 1 ESP, which stands for Emission System Protection. The full synthetic was introduced only recently in CJ-4 form, so there still is little field experience, Wissel says. While some fleets run change intervals as long as 80,000 to 100,000 miles, the maximum interval is “completely dependent on service,” she says.
The risk would be the lower ash limit (total base number) of the new oil. “The TBN numbers have dropped, but the TBN in this oil is more action-packed,” Wissel says. “You get more out of a small amount of mass. As a result, we may well be able to run these very long changes.”
Stede Granger says Shell Rotella T is intended for owner-operators who change their oil at a conservative interval. For those who favor extended oil changes, Shell offers Rimula Super, with a different chemistry that “gives more TBN for the amount of ash,” Granger says. “You can use oil analysis to look at extending drains.”
Different factors may limit the drain interval depending on the engine and the truck’s application, Granger says. TBN might limit one vehicle, while soot accumulation might limit another.
CJ-4 is required to handle significantly more soot than CI-4. This means the soot can accumulate in the oil but remain dissolved by the detergents, so the viscosity will not increase and the oil will not become gritty. Shell has photos of a Cummins pushrod that remained smooth with CJ-4 while a similar engine ran during oil testing on their CI-4 Plus for the same nuber of miles showed obvious scoring.
BP Castrol’s premium High Puron semi-synthetic oil allows users to “double OEM drains if they follow up with oil analysis,” says Steve Goodier, BP Castrol director of technology. Early results show this will work even with 2007 engines, he says.
Unlike most other CJ-4 oils, High Puron’s CJ-4, which uses “ashless TBN boosters,” actually has “a higher TBN than our previous CI-4,” Goodier says. “It’s higher at the start and it retains it better because it’s better than the previous technology.”
Tection Extra, BP Castrol’s conventional oil, is intended for standard drain intervals. “It’s performing extremely well,” Goodier says. “It’s the oil’s extra soot-handling ability that reduces the wear.”
ConocoPhillips is bullish about its oils’ performance. “Our premium CJ-4 products are designed for added features and benefits including extended drain capability, which is proven in field tests and by our customers’ experience in 2007 and pre-2007 engines,” says Reginald Dias, director of commercial lubricants.
PAYING FOR ITSELF
If you don’t feel confident in extending change intervals with CJ-4, how might this new oil save you enough money to justify its higher cost?
LESS OIL CONSUMPTION. The new oil is designed to minimize the amount of oil passing the rings and putting ash into the diesel particulate filter.
REDUCED WEAR. “Indications are that you’ll also get a reduced wear payback,” says Steve Goodier of BP Castrol. The new oil reduces piston deposits, ring wear and liner bore polishing, says Stede Granger of Shell. This in turn can reduce the risk of a breakdown, extend engine life and improve fuel economy.
When these factors are considered, making the switch begins to make a lot of sense to any owner-operator looking for a good million miles before teardown.
“For owner-operators, the bottom line is not measured by the cost of oil alone,” says Reginald Dias of ConocoPhillips. “It is the cost of doing business.”
BIODIESEL MEETS CJ-4
What about running biodiesel and CJ-4? “I’m not worried about 5 percent (B5) fuel,” says Chevron’s Jim McGeehan. “But B20 can cause problems. The content of the oil is looking good when running on ultra-low-sulfur diesel, but there is apprehension about oxidation and increased piston deposits when running biodiesel. On top of the 2007 differences, the biodiesel equation is far more complex.”
For now, the verdict on CJ-4 and B20 biodiesel is the same as that on CJ-4 overall: preliminary. “A year from now,” McGeehan says, “we’ll have a lot more to say.”