Update on PC-11 Engine Oil Specification
by Michael Holloway, CLS, OMA I
North America Sales Manager

A next generation API specification for heavy duty engine oil, currently referred to as Proposed Category 11 or PC-11, is under development. The commercial introduction date is scheduled for December 2016. The focus of PC-11 will be fuel economy and extended drain intervals. It was discovered that lower viscosity engine oil would help increase fuel economy thus using less fuel and lowering emissions. The challenge has been to be able to provide protection performance with a lower viscosity grade oil. The viscosity determination for a lubricated system takes into account operating temperature, surface tolerances, the speed and load to name a few. Using an oil that is the wrong viscosity (too thick or too thin) will contribute to failure. Therefore, it was vitally important that a lower viscosity oil be able to perform. Oil blenders are designing the engine oils for performance upgrades such as permanent shear stability, thermal stability and aeration. Moving from a SAE 15W-40 to a SAE 10W-30 was found to provide about 1% fuel economy improvement. This also had to do with engine design and operating cycle dependent yet it is a significant finding.

In order to put this into perspective, the US consumed 37 billion gallons of over-the-road diesel fuel in 2014. The numbers are startling. A 1% fuel economy improvement would save 370 million gallons of over-the-road diesel or over $900 million in fuel costs annually. When we burn less fuel, we produce fewer emissions. The API-based heavy-duty diesel lubricant specifications for the next several years will be focused on “Total Cost of Ownership”, with objectives for fuel economy, extended service and durability.

The new API classification will be split into two distinct sub-categories. The designations will be CK-4 (PC-11A) and FA-4 (PC-11B). The aim is to ensure that engine durability is maintained with improvements in oxidation stability, aeration, shear stability as well as improved fuel economy.

The CK-4 oils will be formulated to directly replace CJ-4 oil, the most advanced API category now available. These products will conform to the new PC-11 wear-performance standards and will be offered in the same viscosity grades and oil types (conventional, full synthetic, synthetic blend) as CJ-4 oils. And it’s expected that engine builders will consider these oils as fully backwards-compatible, approving them for use in all current vehicles. The CK-4 oils are expected to have improved oxidation and aeration performance compared to CJ-4 oils. They will be fully backward compatible with CJ-4. And can be used in any application where CJ-4 is currently used. The SAE viscosity grades will be 5W-30, 10W-30, 5W-40, 10W-40 and 15W-40.

The FA-4 oils will also have improved oxidation and aeration performance compared to CJ-4 and are designed to provide improved fuel economy. This class will have a lower HTHS viscosity offering than CK-4 oils (SAE 5W-30, 10W-30). These oils will not be interchangeable or backward compatible with CJ-4 oils. The FA-4 oils will be formulated primarily to help boost the fuel-efficiency of next-generation engines while providing the same wear protection. Because of their lower viscosity, the backwards compatibility, as determined by individual engine makers, may be limited. It is advised to consult the OEM or Owner’s Manual regarding use restrictions, refer to any technical bulletins provided by the OEMs or to contact them directly through their distributors.

Most of today’s API CJ-4 oils claim API SM and meet the gasoline engine oil requirements. A fleet with both gasoline and diesel were able to use the same engine oil however, that may not be the case going forward. Not all heavy duty engine oils will meet API SM or API SN classification for gasoline engines. There will be API CK-4 and API FA-4 oils offered that will meet API CK-4/SN or API FA-4/SN, but not all will meet it. If you have a mixed fleet of diesel and gasoline engine equipment, look for oils meeting API CK-4/SN or API FA-4/SN.

OEMs have not yet established drain interval changes for the new API CK-4 or API FA-4 engine oils and drain interval extensions continue to be a competitive battlefield amongst these OEMs. It is important to recognize that a change in engine oil formulation may affect how the oil will perform and react in the working environment. This means engine oil drain intervals should be verified and/or re-established with the use of oil analysis when there is a change in engine oil formulation. And while efforts are being made to ensure the lower viscosity engine oils provide adequate protection for the new engines, oil analysis should always be used to establish proper wear rate trends. Used oil analysis will play a key role in ensuring these new engine oils are effective and used properly.