Know the score on CJ-4
Routine oil analysis has always been prudent, and it’s no different with CJ-4 oil used in 2007 engines because engine stresses are much greater and CJ-4 normally has a slightly lower TBN level. But don’t be surprised if results suggest extending your change interval – CJ-4 is a much better oil and ULSD contains much less acid-producing sulfur.
New oil specifications sometimes can be more exciting to engineers than to truckers. The new CJ-4 oil is better than CI-4 Plus, but it’s also more expensive, so for many owner-operators the switch will not necessarily be automatic the next time they drive into a service bay, or the moment that case (or barrel) of CI-4 Plus in the home shop is depleted.
The new oil is ideal in a nation where nearly all diesel fuel now contains only 15 parts per million of sulfur. Even if you’re running older trucks and have access to diesel that meets the previous standard of 500 ppm sulfur, that diesel soon will be impossible to get; it’s not being replaced as it’s drained from the system nationwide.
The downside to CJ-4 is a slightly higher price in most cases. Depending on the brand, the new oil could be the same price or anywhere from 75 cents to 85 cents more per gallon, or 20 percent higher, according to anecdotal reports from three companies in the supply chain.
If your truck is older, with no diesel particulate filter and maybe no exhaust gas recirculation either, CI-4 Plus “might be the best way to go,” says Eric Olsen, staff engineer with Chevron Global Lubricants.
But for low-emissions engines with a DPF, the higher cost of the new oil may be more than made up for in savings from improved fuel economy and fewer DPF cleanings.
“Low-emissions engines are making life a bit more complicated,” Olsen concedes.
One reason for the CJ-4 formulation was the need to limit the amount of sulfated ash, the stuff that comes along with additives used to neutralize acids and protect surfaces in the newer, higher-stress engines. While the carbon soot trapped by the DPF burns, ash accumulates. This blocks the flow of exhaust through the porous ceramic of the DPF.
“Keep in mind that DPF plugging is a matter of degree,” Olsen says. “Well before plugging gets bad enough to cause complaints of power loss, the increased backpressure has been hurting fuel economy. This is among the myriad of reasons that the majority of OEMs recommend API CJ-4 for 2007 and 2008 model year engines.”
Cummins has approved the use of CI-4 Plus in its 2007 engines, which Olsen sees as acknowledgment that fleets want to stock only one engine oil. Since most will own relatively few trucks with DPFs for quite some time, CI-4 Plus seems a logical choice – for now.
The industry generally believes that using CI-4 Plus won’t damage the DPF, but simply will cause it to need more maintenance. However, some engine manufacturers now require CJ-4 under their warranties.
If you’re a small-fleet owner who has some trucks with DPFs and some without, you need to stock two oils, use CJ-4 across the board, or make sure your DPF-equipped engine manufacturer approves CI-4 Plus – assuming you think what you save on oil will more than pay for any increase in DPF maintenance and fuel costs. The simplest route, of course, is an across-the-board upgrade.
Having to reduce sulfated ash in the oil produced by the new engines might have thrown refiners and fleets into a panic but for the change in diesel fuel that came along with DPFs. The nationwide switch from low-sulfur diesel to ultra-low-sulfur diesel was required to help meet the U.S. Environmental Protection Agency’s 2007 standard for airborne particulate, a.k.a. soot. That’s a relief, because unlike ash, sulfur actually will damage the DPF, interfering with its ability to catch and burn off particulate.
The switch in fuel also cuts the industry a break on acidity. The total base number of an oil, or TBN, tells how much acid-fighting capability it has. Most of the additives that combat acidity in the oil tend to create ash. Had all the factors that create acid in the oil stayed the same, fleets and oil refiners might have been faced with a subtle compromise in oil life and shortened change intervals – or significantly higher cost – to provide exotic, low-ash TBN additives. But drastically cutting the amount of acid-generating sulfur takes a tremendous amount of stress off the oil, which is one reason why CJ-4 actually has a lower TBN than its predecessor.
“We have found that the low sulfur in the fuel contributes to less acid buildup,” says Walt Silveira, U.S. technical manager with Shell Lubricants. With less acid to fight, you need less total TBN. For good measure, CJ-4’s superior stability also works to prevent acid buildup, Silveira says.
“TBN retention is now the name of the game,” says Yeong Kwon of ExxonMobil Commercial Vehicle Lubricants. “We optimized our additive system to maximize the amount of protection and minimize the amount of ash. Initial TBN can be lower, but it’s retention that counts.”
“This is an aspect of low emissions that is making life easier for the lubricant,” Olsen says. “If everything else were equal, except for fuel sulfur, lower sulfur would mean longer drain intervals, and fleets could save money by optimizing drain intervals.”
Even if you still are using CI-4 Plus, therefore, you should have your oil analyzed by a good lab to see whether you can lengthen your change interval just because of the change in diesel fuel.
Acid buildup also is aggravated by heat, so in the latest high-temperature engines, coolant maintenance especially is critical. “The oil and coolant work together,” Silveira says.
What if you own only pre-2007 trucks, even pre-EGR trucks? Should you just keep using CI-4 Plus? Not necessarily. Some refiners say they have the numbers to prove that spending a few pennies more for oil can save you money by allowing longer change intervals, as well as improving engine life and reliability.
“We have seen at least one example of a fleet that was changing at 30,000 miles that went to 40,000 miles,” Kwon says. “Those who have been able to extend changes have been reaping the fruit of the endeavor that created the performance enhancements required to meet the suite of tests required by CJ-4.”
One fleet had a variety of engines – ’07, pre-’07, even pre-EGR – and nevertheless was able to extend changes across the board, Kwon says.
“Lots of this kind of data is coming through, but you need to evaluate fully,” Kwon says. “No one can make a sweeping generality. What you can do depends on drive cycle, load and other such factors.”
“We’ve seen some good performance and high reliability for both ’07 and pre-’07 EGR engines,” Silveira says. “CJ-4 performs well in both applications. There are even a few fleets that have run intervals out to 35,000 to 45,000 miles. They have seen no change in reliability, wear, TBN or deposit control. The oil performs well and protects the engine.”
He cautions, however: “Most big fleets are not trying to go that far.” They’re content with the manufacturer-recommended change interval, bolstered by good oil-analysis reports.
The claims for special formulations are bolder. BP Castrol’s semi-synthetic Hypuron premium CJ-4 diesel engine oil “was deliberately formulated for extended drain, with the idea that doubling the drain might be practical for many fleets,” says Steve Goodier, director of technology.
Another special formulation is Mobil Delvac 1 ESP, which stands for Extended Service Protection. Kwon calls it the first 5W-40 fully synthetic CJ-4. “We have some customers on very long change intervals, and they have been able to remain at that extended drain.”
“Extending changes is never a simple question to address,” Goodier warns. “Is the engine used on highway or in a vocational application? You can’t just start using Hypuron and extend. We depend on an analysis program. Only that kind of data will tell you whether or not you can extend safely.”
That’s not the only reason to do oil analysis. “With an analysis program, whether you have a coolant leaking into the oil, a bad injector leaking fuel into the oil, or a leaking air filter, you can repair the problem and prevent damage,” Goodier says.
For Silveira, the value of CJ-4 is not in extending changes but in long-term engine protection and lower maintenance cost. “There is enough value there,” Silveira says. “The benefits include engine cleanliness and wear performance, deposit control and reduced oil consumption.” CJ-4 is consumed more slowly than its predecessors by design, because lower consumption means less ash in the DPF, Silveira says.
Working closely with one fleet, Shell anticipates reduced wear and deposits as engines accumulate many miles on CJ-4 – and the more numbers are generated, the more truckers will make the switch. “Selling truckers on CJ-4 takes education,” Silveira says.