Know the score on CJ-4

| December 12, 2008

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.

Comments are closed. strives to maintain an open forum for reader opinions. Click here to read our comment policy.