Finished Lubricants

Heavy-duty Upgrade Takes Shape


PC-11, the heavy-duty engine oil category upgrade being developed by diesel engine manufacturers and the lubricants industry, continues to make progress towards its April 2016 market debut. Meeting Jan. 30 in Chicago, the New Category Development Team voted on the most critical tests that must be included in the coming category – and also debated whether a new SAE viscosity grade might best ensure that these oils deliver their promised fuel economy in diesel trucks.

One of the primary tasks facing this group, which is chaired by Dan Arcy of Shell, was to agree on the slate of engine tests that should be included in the oil category. Three new engine sequence tests had been proposed, one each from Volvo/Mack, Caterpillar and Daimler.

Sponsors of Macks T-13 test for thermal stability and oxidation and Caterpillars Aeration test said these tests were ready for inclusion in PC-11, and both were voted in to the new category. Both tests already had the support of the American Chemistry Council, which represents lubricant additive companies. Reportedly, the industry already has almost a dozen T-13 test stands installed, and three Aeration test stands.

Daimlers DD13 test, which is intended to measure piston and liner scuffing wear, presented a more knotty issue. The additive companies had not accepted this test yet, and the engine manufacturers themselves acknowledged that its reproducibility and repeatability are not ideal. Although Daimler expressed confidence that the test can be ready in time for PC-11, it asked for more time to complete its development work, so the New Category Development Team voted to not include the DD13 at this time. It still could be added later.

Holdover Tests

In addition to the new tests above, PC-11 will carry over seven more engine sequence tests from todays API CJ-4 heavy-duty engine oils, notes Jim McGeehan of Chevron. McGeehan, who is an API representative to the NCDT, described the holdover tests in a Jan. 23 presentation to the 19th International Colloquium Tribology, at Germanys Technische Akademia Esslingen. They are:

General Motors roller-follower wear test, which measures the oils ability to control abrasive and rolling valvetrain wear due to engine soot.

The Cummins ISB valvetrain wear test remains, too. Cummins had experienced field failures with its ISB engines, and this test resolved it, so its back in for PC-11, McGeehan observed. It zeroes in on soot-related cam and tappet sliding wear.

The Cummins ISM test evaluates abrasive and corrosive wear in injector screws and valve stems. Oils also will need to minimize sludge and extend filter life to pass this one, McGeehan remarked.

The CAT C13 test demonstrates how well an oil controls iron piston deposits and oil consumption, and runs the longest of all the heavy-duty engine tests – 500 hours.

The Caterpillar 1N test also measures deposit control and oil consumption, using aluminum pistons.

Macks T-11 test measures an oils viscosity control and how well it stands up to soot agglomeration.

The Mack T-12 will continue to be used to measure ring and liner wear, and will also get a new merit rating system for determining if an oil passes or fails. This test previously looked at oil oxidation as well, but not any more, McGeehan said, as that parameter will be handled by the new Volvo/Mack T-13 engine test. However, the T-13 does not develop significant levels of soot, so it cannot distinguish liner wear – and thats why the T-12 remains in the category, McGeehan pointed out.

He added that PC-11 has the same chemical box as current engine oils, with ash limited to 1.0 weight percent, sulfur 0.4 percent, and phosphorus 0.12 percent. Noack volatility is going to be tighter, too, going to 13 percent for all grades. (It currently is 15 percent for SAE 10W-30 diesel oils.)

Matrix Millions

The next PC-11 hurdle will be a precision matrix for the new engine tests, which involves repeated runs of the fired engine tests – a very expensive proposition. Steve Kennedy of ExxonMobil, speaking for the PC-11 Funding Group, advised the NCDT meeting that only about $2 million to $2.5 million is available to defray matrix test costs, and his group hopes to get API, ACC and EMA to share equally in the expense. If EMA, the Truck and Engine Manufacturers Association, would contribute more, so would API and ACC, he believes. Two independent engine test laboratories, Southwest Research Institute and Intertek Automotive Research, also said they will try to fill a gap in funding by providing discounts of up to 10 percent on the matrix tests.

The meeting also wrestled with the issue of how to best differentiate the new oils for consumers. It has been known for a while that PC-11 will actually be two oil categories. PC-11A will cover current viscosities like SAE 15W-40 and will be backward compatible with earlier oil categories, including todays API CJ-4 oils. PC-11B will address lighter diesel grades, such as SAE 5W-30 and 10W-30, and enhance their fuel economy contribution by focusing on their high-temperature high-shear viscosity. These lighter-weight oils would be suitable for future diesel power plants, beginning with the 2016 model year, but not necessarily for older engines.

The American Petroleum Institutes Lubricants Group in September had discussed the ongoing question of how to most clearly label the difference between these two specifications. For PC-11A, the Lubricants Group is comfortable with a likely designation of API CK-4, which continues the current progression of letters associated with its heavy-duty or C category. For the PC-11B category though, discussions centered on how to establish an evergreen category while minimizing the number of characters, and while clearly differentiating between PC-11A and PC-11Bs distinct viscosities.

The New Category Development Team took up this discussion at their Jan. 30 meeting. There seems to be little debate that PC-11A will continue to have a minimum 3.5 cPs HTHS viscosity limit, as is the case with CJ-4 and earlier oil categories. This provides the needed backwards compatibility for existing engines in on- and off-road applications. However there is a recognition that SAE XW-30 oils should provide fuel economy benefits versus SAE 15W-40, and that will be done by reducing the oils high-temperature high-shear viscosity.

Engine builders say they need to wring as much fuel economy as they can from the new oils, especially as the United States phases in heavy-duty fuel economy standards by 2017. However, they also want assurance that PC-11B wont sacrifice engine durability. One way to achieve this, the meeting heard, may be with a new viscosity grade tentatively referred to as SAE 26, which would be defined using either HTHS viscosity between 2.9 and 3.2 cPs or by kinematic viscosity of 9.3 to 10.5 cSt at 100 degrees C, which is an unusually snug range. This might result in a more limited backwards compatibility which would be OEM, engine and application dependent.

Another SAE Grade?

Pursuing this idea will first require drafting a formal proposal to SAE to amend its engine oil viscosity classification system, SAE J300. This issue should go to APIs Lubricants Group for action, the development team decided.

The upside of a new SAE grade would be even better fuel economy than current SAE 15W-40 while being distinctly different, advocates said. It also would allow the API category (CK-4) to be uniform across all grades, allow the performance nomenclature to remain evergreen, and open the way for subsequent categories (such as CL-4 and beyond) to cover additional heavy-duty viscosity grades such as SAE XW-20. This scheme also maintains the naming consistency of the other previous categories. For consumers, it means that they can continue to order products by brand name and viscosity with confidence they will be getting the oil that their vehicles need.

The NCDT meeting also discussed the actual nomenclature of the PC-11 category, given the inclusion of both higher and lower viscosity products. After a review of seven options, the group felt that two might be suitable. One would be to use API CK-4 as the name for both higher and lower HTHS viscosity products – with the proviso that the former would be backwards compatible while the latter would not. The other proposal, and the one that seemed to garner the most support, is to call the higher viscosity product CK-4 and the lower viscosity product DK-4. The same caveats on backwards compatibility would hold, with the D version offering a parallel path and co-existing with CK-4. The issue now goes back to APIs Lubricants Group for review.

The New Category Development Team meets next on Feb. 26, after this issue goes to press, and has a pretty intensive schedule for the rest of the year as well.

Normally it takes about five years to develop a category, Chevrons McGeehan explained in Germany. The next steps, beyond the precision matrix, will be to finalize all test limits, and then have a demonstration period so that additive and oil companies can kick the tires on the various formulating options. Once thats done, and limits are voted into effect by API, final tests and licensing of actual candidate products can proceed.

When its all complete, we will have a new category, PC-11, and API will begin licensing the oils in April 2016, McGeehan said.

Or will it? At the Jan. 30 meeting in Chicago, NCDT member Luc Girard, of Petro-Canada, noted that theres a lot of work to be done in the next two years. For one thing, the specification still doesnt include guidelines for base oil interchange and viscosity grade read-across, and without these guidelines, the cost of obtaining PC-11 licenses will climb sharply.

One proposal before the NCDT would have PC-11B licensing proceed as scheduled, while delaying the PC-11A roll-out until mid-October 2017. This would help ease the funding and testing crunch, and allow development of more robust engine tests. No decision was made on this suggestion – so for now the April 1, 2016 deadline is still the one to beat.

Lisa Tocci also contributed to this article.

Related Topics

Finished Lubricants