The formation of a new oil category (PC-11) is not something to be taken lightly. “For each of the additive suppliers or oil companies to finalize all of their formulations, the total cost of this type of project is extremely expensive,” says Jim McGeehan, global manager of diesel engine technology, Chevron Lubricants. “It does not come cheap, but in the end, it pays for itself in that lubricants are not causing engines to fail.”
In the past couple of decades, diesel engine emissions regulations necessitated changes to heavy-duty diesel engine oils. “Each time there has been a change, with the exception of 2010, there has also been a change in the type of lubricant necessary to lubricate those engines,” says Dan Arcy, Global OEM technical manager for Shell and a member of the American Petroleum Institute (API) committee to develop the PC-11 oil category.
Last year, the National Highway Traffic Safety Administration issued a regulation that limits greenhouse gases and mandates fuel economy improvements for the first time in medium- and heavy-duty trucks. These rules phase in from 2014 to 2018.
Truck manufacturers have different technologies that can be used to meet these requirements. One is the use of low-viscosity, fuel-efficient engine oils. While thinner oils reduce parasitic losses and increase fuel economy, concerns can arise in regards to the ability of the oil film to adequately protect critical surfaces. These low-viscosity engine oils must provide the same durability as current oils, which makes development of a new oil classification necessary.
“Previous categories were driven first by engine durability, then they went to aftertreatment compatibility with CJ-4. But this is now a new dimension — fuel economy,” says McGeehan.
Oils must Evolve with Engines
Prior to CJ-4, development of new oils were strictly focused on engine durability. CJ-4 added the requirement of aftertreatment compatibility.
“CJ-4 limits the chemical composition of the fresh oil in order to minimize incombustibles in the particulate filter to ensure it has maximum life before its cleaning,” McGeehan explains. “With CJ-4, there is a chemical box that limits the oil’s sulfated ash, phosphorus, sulfur and volatility. That requirement put in place for CJ-4 will be the same for PC-11. There is no change in the chemical box.”
However, since the introduction of CJ-4 oils in 2007, engine designs have evolved. “The pressures in the cylinders have gone up. The metallurgy inside the engines has changed. The coatings on parts within the engine are different,” Arcy points out.
In addition, the CJ-4 oil specification has been the prevailing standard longer than any modern diesel engine lubricant category. “The API came out with CJ-4 in October of 2006,” Arcy recalls. “The testing procedures used to qualify CJ-4 type oils may not be the most representative of the current engines and hardware in the field.”
Engine test obsolescence is also becoming an issue. “There will be no parts available to run some tests [needed to qualify for CJ-4] around the 2015 time frame,” says Arcy. “We could develop new tests to replace the ones that are there. But when you go to the cost of developing a new test, you want to make it with current hardware and you want to make sure it is viable for the new engines coming out.”
Defining the Category
In June of 2011, engine manufacturers requested the API develop a new oil category to meet the demands of engines in development. They wanted oils that could help reduce CO2 and improve fuel economy. They requested improvements in oxidation stability, resistance to aeration, biodiesel compatibility, a scuffing and adhesive wear test and increased shear stability.
Upon receiving the request, the API established a new category evaluation team. This team works with the engine manufacturers, additive industry and oil marketers to determine if the request is warranted.