LUBRICANT manufacturers created the CI-4 engine oil category to meet the demands of the post-October 2002 diesel engines, but older power plants also benefit. The CI-4 oils offer the potential for extended drain intervals, reduced need for make-up oil, lower operating costs, and longer engine life.
CI-4 oils are quickly replacing the previous CH-4 category throughout the North American market, and the price differential reportedly is less than 5%. Under development since the early 1990s, the new oil category was needed to meet the challenges of lower emission diesel engines, many of them equipped with cooled exhaust gas recirculation (EGR) to meet the Environmental Protection Agency exhaust regulations that took effect October 1, 2002.
EGR routes a portion of the engine's exhaust through an intercooler and back to the intake manifold, where it is mixed with fresh, filtered air and sent into the cylinders. This blend of spent and unspent gases results in lower peak-flame temperatures and less NOx.
However, there are some unpleasant side effects with this arrangement. Soot, heat, and acid are just a few of the byproducts of combustion, and all pose threats when reintroduced to internal components of the engine.
Increased soot levels, unless adequately dispersed, can cause oil thickening, sludge, clogged filters, and accelerated engine component wear through abrasion. Higher amounts of soot also can cause loss of low-temperature pumpability, preventing the oil from freely flowing through the engine and protecting critical contact surfaces.
“A couple of years ago, before extensive field testing had been done, some industry experts were predicting soot levels of 8% to 10% — more than double the amount generated in [the pre-October 2002] engines,” says Michael Ragomo, commercial vehicle lubricants advisor, ExxonMobil Lubricants & Specialties Company. “Fortunately, these early projections now appear to have been too high. At least one pre-production engine, in fact, generated less soot than its non-EGR next-of-kin.”
The other concerns regarding EGR-equipped engines — acid and heat — remain serious threats. Sulfurous and sulfuric acid are natural byproducts of spent diesel fuel. In addition, research data shows that internal engine operating temperatures with EGR can be as much as 20 to 30 degrees higher than is found in non-EGR engines.
All of these factors demanded a much more robust engine oil, and the CI-4 category was the result. The new oil category applies to light-, medium-, and heavy-duty diesel engines produced after October 2002 and is “backward compatible,” meaning that an oil meeting CI-4 is automatically accepted as an alternative to CH-4.
While many of the new oils on the market meet minimum CI-4 requirements, performance quality differs between manufacturers as a result of variations in their formulations. Heavy-duty engine oils formulated from Group I base oils will have the greatest difficulty meeting the new standards because they have lower soot dispersion capability and poorer antioxidant response. Group II and III base oils are premium-quality and work more effectively with soot dispersing additives. Additionally, these base oils are more likely to exceed the new CI-4 requirements by the greatest margin.
While good soot dispersion capabilities are crucial, the characteristics that address heat and acid factors may be even more important. CI-4 oils are formulated to a lower volatility limit, a way of measuring how much oil burns off at high temperatures. The burnoff creates deposits in the engine. Additive packages in the CI-4 oils also help control the oxidation that results from high engine temperatures, as well as heat-related thickening.
Oxidation contributes to the formation of acids in engine oil, which must be able to neutralize the buildup. The quality of the base oil and the additive package determine the ability of the engine oil to counter the corrosive effects of acids. A good formulation results in longer bearing life and lower wear metals over the life of the engine.
“Fleets need to select a CI-4 oil with an ample alkaline reserve,” says Dan Arcy, products marketing manager for Shell Lubricants, which includes Shell, Pennzoil, and Quaker State products. “The alkaline additives act like a Tums for the engine, neutralizing pH levels and preventing corrosion.”
Arcy adds that so many improvements were made that the CI-4 category clearly is a much stronger and more durable engine oil. It is such an improvement that it could reduce the need for synthetics in some fleet applications.
In terms of the ability to handle higher engine temperatures, the gap between CI-4 and synthetic oils has been narrowed. However, fleets that operate in extremely low temperatures still will benefit from synthetics, Arcy says.
Extended drain intervals (30,000 miles and higher) are possible for trucks in longer haul operations. “The greater wear protection in the CI-4 oils makes this a possibility,” Arcy says. “The best candidates are fleet operations with a great deal of consistency.”
He cautions against extended drain intervals for stop-and-go operations or those with high amounts of engine idle time. Extended drain intervals should be avoided in operations with fuel economy below six miles per gallon.
Oil analysis is crucial with any effort to extend the drain intervals in older engines, according to Greg T Raley, commercial products manager, Shell Lubricants. Oil analysis is especially important in the new EGR engines, which have a very limited track record.
“The new engines need some study,” Raley says. “We're going to have to wait and see what the proper drain intervals should be. Oil analysis will enable fleets to reach reliable conclusions, and we recommend it for every new EGR engine that is put into service.”
Fleets need to pay close attention to soot levels, as well as monitoring total base number (TBN) for signs of oxidation. Wear metals, contaminant metals, and additive metals should be watched.
“One of the biggest benefits of oil analysis is something that has nothing to do with the new EGR engines,” Raley. “Analysis detects glycol (antifreeze) leaks in the engine. A glycol leak will destroy an engine faster than anything else.”
Seven basic tests should be a part of any oil analysis program, according to Kevin Fitzgerald, vice-president of marketing for Castrol Heavy Duty Lubricants Inc. These critical tests include contaminant metals, fuel, glycol, soot, viscosity, wear metals, and water.
Even as the trucking industry comes to grips with the new EGR engines and CI-4 oils, lubricant manufacturers are moving on to the next stage. Work is underway on Proposed Category 10 oils. Due out in 2006, PC-10 will set the standards for oil to be used in 2007-model diesel engines.
These engines will be required to burn ultra-low-sulfur fuel. They will need new exhaust aftertreatment technology and other possible emissions-reducing hardware. Some members of Congress are pushing for still more emission requirements.
“Engineers say the challenges to reach the next level of oil performance are daunting and could require a whole new batch of additive chemistry,” Ragomo says. “These new oils may not be compatible with engines other than the ones that they are specifically designed to lubricate. It's hard to say what will happen between now and when PC-10 is formally approved as CJ-4.”