SAN DIEGO — Last week, the New Category Development Team took up the ticklish issue of how to label the coming diesel engine oil upgrade for consumers. The upgraded category, known as PC-11, will need two distinct names under the American Petroleum Institutes licensing system. One could follow the familiar API C series, but the other version must be flagged clearly as a fuel-economy specification for the latest-model engines — not for existing and older heavy-duty diesels.
Convening here Dec. 9 during the ASTM Committee D2 meeting, the oils development team, chaired by Dan Arcy of Shell, was reminded that prior categories posed less difficulty since their viscosity grades were in alignment with traditional SAE J300 viscosity limits.
However, PC-11 presents a fresh dilemma since it will be two categories in one. PC-11A will be the normal engine oil, totally backwards compatible with earlier API categories. This version is likely to be called API CK-4, succeeding the current API CJ-4 category.
Its cousin PC-11B will have a lower high-temperature, high-shear rate (HTHS) viscosity to offer some improvement in fuel economy. However, there is likelihood that it may not be fully backwards compatible as preferred under APIs Engine Oil Licensing and Certification System, so PC-11B oils cannot simply take up the next letter in the API C sequence.
The naming issue has been discussed for over a year, with several means proposed for differentiating the two oil subcategories. One early proposal came from EMA, the Truck and Engine Manufacturers Association, which asked that each version have improvements in oxidation stability, aeration and shear stability. The major difference between the subcategories is their HTHS limit.
For SAE 10W-30 viscosity oils, HTHS viscosity will be set at a minimum 3.5 centiPoise for PC-11A, and at a lighter 2.9 to 3.2 cP for PC-11B. The oil industry has expressed concern that there is insufficient difference — just 0.3 cP — between the PC-11A and PC-11B HTHS specifications to allow for a reasonable blending tolerance when making the finished oils. Retailers have also voiced concern over having two versions of the same viscosity grade on their shelves.
Although SAE 10W-30 oils currently represent a small percent of North Americas heavy-duty engine oil sales — about 6 percent, according to the additive company Infineum USA — sales are growing rapidly as more engine manufacturers recommend this grade to capture fuel economy benefits.
EMA confirmed that ACEA (which writes oil specifications for European vehicles) was setting the HTHS limit for XW-30 multigrade oils at 3.2 cP to assure fuel economy. There are no general data supporting this viscosity; however, Volvo Powertrain has data demonstrating a benefit, and has incorporated 3.2 cP HTHS in its own Volvo engine oil specification.
The New Category Development Team had requested guidelines from the API Lubricants Group for naming the two sub-categories. The Lubricants Group responded that for the high HTHS version (PC-11A), it was comfortable with the category name API CK-4. For the low HTHS version (PC-11B), the discussion centered on how to establish an evergreen aspect for future categories.
Criteria for oil marketers included minimizing the number of characters that must be displayed, while maintaining a distinct difference between PC-11A High Vis and PC-11B Low Vis. The API Lubricants Group also preferred to see an evergreen name or symbol and asked that the low-viscosity oil not sound like the high-vis oil.
After testing several naming options within the NCDT, agreement was reached on the following system:
PC-11A oils are to be designated as API CK-4, while PC-11B oils would be designated as API FA-4.
In addition, an H or L would be added to the SAE XW-30 viscosity grade to clearly differentiate the fuel economy (L) and non-fuel economy (H) sub-grades. The following are proposed API service symbols demonstrating how the marks would look. API’s Lubricants Group will need to approve the designations as well.
PROPOSED SERVICE SYMBOLS
The question of having SAE XW-30 in both H and L versions was presented by Dan Arcy to the SAE J300 Engine Oil Viscosity Classification Task Force the following day, to weigh its concurrence with the concept. The J300 Task Force responded that it was an acceptable proposal, provided there was broad market support for it.
SAE also would have to vote to modify its J300 standard to incorporate the L and H definitions before the proposal could be finalized.
The New Category Development Team is made up of representatives from API, EMA and the American Chemistry Council (which represents additive companies). It also invites input from JAMA, ILMA, ASTM, SAE International and Europes CEC to help manage the engine oil development process, following a consensus process.