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Last month I gave you an update on ILSAC GF-6, the new gasoline engine oil category slated to see first use in the market by Sept. 30, 2016. This month, I want to close the circle by bringing everyone up to speed on the new PC-11 diesel engine oil specification, also expected to be in effect in 2016.

The American Petroleum Institutes PC-11 New Category Development Team, ably chaired by Dan Arcy from Shell, is meeting regularly to review the new tests that will be required for this latest iteration in heavy-duty engine oils, as well as to ponder how the oils should be labeled for consumers. By the end of the groups April 25 meeting, a number of decisions had been reached or were taking shape on the anvil.

Not surprisingly, whats happening with GF-6 impacts PC-11. Specifically, the Auto Oil Advisory Panel, which is directing the light-duty category development process, has strongly recommended that PC-11 products which want to claim universal oil credentials – that is, suitable for servicing both gasoline- and diesel-fueled vehicles – must meet the full physical and chemical limits of ILSAC GF-6.

One of the most critical of these is GF-6s phosphorus limit, which is 800 ppm max. The automakers are concerned that if universal oils are allowed to have more phosphorus than that – as heavy-duty diesel oils and the regular API S-category oils do – the oils will poison their emissions systems.

The Engine Manufacturers Association, the trade group which represents heavy-duty engine builders, supports this position. They also have been concerned for some time that universal oil formulations can lead to compromises in performance.

For those of you who dont remember the genesis of the universal oil concept, there was a time when commercial fleets had a mix of gasoline- and diesel-fueled vehicles. So universal oil was introduced to reduce inventories and avert worries about product mix-ups in the service bays; only one oil needed to be stocked, and it could go satisfactorily into both types of powerplants.

Over the past 20 years though, the lubrication requirements of diesel and gasoline engines have diverged to the point that a single oil is hard pressed to meet all requirements. Couple that with fleet choices that are primarily diesel-powered, and universal oils arent as desirable as before. Itll be fascinating to watch how this plays out.

Sharpening the Focus

Meanwhile, the mix of tests that will be required for PC-11 candidate formulations has changed some from the initial proposal. Originally the Volvo T-13 test was to replace the Volvo T-12 test for evaluating ring and liner wear and bearing corrosion and oxidation. (Yes, the T-12 and T-13 tests are now referred to as Volvo tests rather than Mack. Of course, that is a reflection of Volvos acquisition of Mack several years ago.)

The New Category Development Team has determined that both the T-12 and T-13 tests will be required. Work continues to define the new T-13 test, but liner wear will not be a parameter in this test. That is why the T-12 will not be replaced. So far, the T-13s oxidation performance appears to be responding well to changes in temperature, but work is still going on to balance this tests length, severity and engine durability parameters by adjusting temperature and pressure parameters.

Biodiesel compatibility, which seemed a key requirement once, has been dropped from PC-11. There are several reasons for this action, according to Ken Chao from John Deere, who chaired the task force on this need. Biodiesel quality has improved over the years, which means fewer field complaints from our customers, he noted. However, he added, the main reason for dropping this requirement is the slow progress on tests being developed in Europe, which the New Category Development Team had hoped would meet the PC-11 timeline. For now, EMA has decided to take a wait and see position on biodiesel compatibility testing.

Two Categories in One

PC-11, as earlier columns explained, will come to the market as two categories. One will have the same viscometrics as earlier categories so its backwards compatible, and the other will define a lower-viscosity oil designed to capture improved fuel economy. How is this progressing? For the fuel-economy oils, EMA decided to accept the high-temperature high-shear limit (@150 C) of 2.9 to 3.3 centiStoke. In addition, Noack volatility will be limited to 13 percent maximum for all viscosity grades, which will help assure that evaporative losses dont lead to unacceptable oil thickening.

Splitting PC-11 in two presents an interesting dilemma: To date, a way to label the new lower-HTHS viscosity SAE 10W-30 grade PC-11 oil has not been determined. It sure wont be backwards compatible with earlier categories, since the HTHS viscosity will be lower than that set for API CJ-4 and its predecessors. Yet possible naming conventions are still not emerging.

Progress on Tests.

As for engine sequence tests to demonstrate PC-11 performance, how are they doing? Besides the Volvo T-13, these include the Daimler DD13 test to measure piston/liner scuffing wear; a Caterpillar C-13 engine oil aeration test; and a Caterpillar Single Cylinder Oil Test Engine, or Scote, for gauging diesel oil oxidation resistance.

The Daimler DD13 test is very important to EMA since there is general concern about piston and liner scuffing when using lower viscosity oils. So for that low-vis PC-11 category in particular, you can expect to see stiff test criteria that address scuffing. Currently, the DD13 is undergoing fine-tuning to cut down on test length. It is on schedule to be ready for acceptance into matrix testing in September.

The Caterpillar C13 oil aeration test is progressing as well, and continues to show good discrimination and repeatability. A low-HTHS version of one of the development oils is being run, and Reference Oil 1005 will be run as well for comparison to the current aeration test. At I write this in late May, the test development is still on schedule to be available for the industry testing matrix in June.

The Caterpillar Scote test is not as far along. Jim McCord of Southwest Research Institute in late April reported that work to develop the test procedure is continuing. The current test conditions are running close to engine failure, so efforts are under way to modify the test conditions and slow failure mode. Theres no question that oil oxidation is occurring and that pressure differential scanning calorimetry is considered a good predictor of oil oxidation. However, its unlikely that a test will be available by the time you read this.

EMA has been tasked with insuring that none of the test measurements from any of these proposed tests are in conflict with each other. That would stand to reason!

Money Well Spent?

Whenever a new engine oil category is developed, there is always hope that some new tests will make older tests redundant and therefore unnecessary. A task force led by Navistars Heather DeBaun was set up to evaluate the need for two older tests, the roller-follower wear test and the Caterpillar 1N. She reported in April that the Redundancy Task Force concluded that there is no test redundancy, so both should remain a part of PC-11. Too bad, since that means extra testing (and cost).

DeBaun also highlighted the status of work on a shear-stability test procedure for PC-11. Field tests continue on five oils selected to represent the range of viscosities and shear stabilities that will likely be available in PC-11 oils. The results will be used to decide on a bench test (probably the Kurt Orbahn Injector Shear Stability) and develop limits.

Naturally, all of this development work comes with a cost. Steve Kennedy from ExxonMobil noted that the New Category Development Team had raised the question of funding for the development program. The funding group met in late May to move forward on an approach for funding PC-11 precision, base oil interchange and viscosity grade read-across testing, based on trade association input on available resources.

The group also discussed matrix design; that is, how and how many tests must be run to establish the precision and repeatability of PC-11s engine tests. The Precision Matrix Task Force, chaired by Rodney Walker from Safety-Kleen, had requested input on this from the American Chemistry Councils Petroleum Additives Protocol Task Group. What, the task force asked, is the minimum number of tests (and their cost) needed to determine PC-11 precision, given a design scheme of six test stands and four labs and either one or two reference oils?

The additives group responded that the proposed PC-11 precision/BOI/VGRA matrix for the new tests prices out at about $8 million. Thats a big number, so ACC is looking at alternate proposals. An initial look at running only precision on the new tests (i.e., no BOI or VGRA) looks to be around $5 million. Furthermore, ACC is evaluating the need for running the new low-viscosity oils through at least some of the older tests. So costs could rise, but not doing tests on the low-vis oils also raises a red flag.

The New Category Development Team agreed that there is urgency here. The deadline for program budgets was June, so it aimed to reach a resolution at the late June ASTM meeting in Montreal.

The process continues and the milestones seemingly are being met. But, as Gilda Radner used to say on Saturday Night Live, Its always something! Keep your fingers crossed that something doesnt jump up to bite us.

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