PC-11 and GF-6: New engines drive change in oil specs
The challenge now is developing tests to deal with the radical transformation in motors and components.
• Two new regulations necessitated groundbreaking specifications.
• Of particular interest is the contribution of lubricants to fuel economy.
• Subcategories for each regulation address backward compatibility issues
BIG CHANGES TO ENVIRONMENTAL REGULATIONS and engines mean big changes to lubricants. This is why it is no coincidence that there are two new oil specifications on the horizon at the same time: PC-11 for heavy-duty diesel engines and GF-6 for passenger automobiles. For each specification (and for the first time), there are likely to be two versions: one for current and future engines and another compatible with older engines. Consumers and maintenance workers will have to be on their toes.
Given that the purpose of oil specifications is to prevent in-use performance issues, the historical absence of any major issues with oil when it’s used as specified is a strong indicator of the strength of the current specification development system.
Joan Evans, Infineum industry liaison advisor, explains, “For both PC-11 and ILSAC GF-6, there are urgent needs to develop new tests to replace those for which the current hardware will shortly no longer be available. In addition, there is a need to develop new tests to evaluate lubricant performance in emerging hardware platforms. Engine hardware design changes are being dictated by the need to improve fuel efficiency and reduce emissions to meet stringent new environmental regulations.”
In 2011 the National Highway Traffic Safety Administration (NHTSA) issued a regulation, which phases in from 2013 to 2018, that limits greenhouse gases and for the first time requires fuel economy improvements for medium and heavy-duty trucks. This was a primary driver for PC-11. In June 2011 the Engine Manufacturers Association (EMA) asked the American Petroleum Institute (API) to develop a new lubricant category for heavy-duty diesel engines that were being developed. PC-11 (PC stands for proposed category) will offer performance beyond the time-tested API CJ-4 engine oils.
The CJ-4 oil specification, introduced in October 2006, has been the standard longer than nearly all diesel engine oil categories. But since October 2006, engine designs have changed significantly. For example, many engine parts are made of different metals, and cylinder pressures have increased. The need for PC-11 was driven by:
• Proposed U.S. government regulations on fuel economy and CO2 emissions.
• Increasing biodiesel use.
• The need for improved protection from higher engine temperatures.
• The need for improved shear stability.
• The need for adhesive wear protection.
• The need to reduce or eliminate engine oil aeration.
EMA requested that the new category for lubricants be split into separate and distinct subcategories, one that preserves historical heavy-duty criteria (higher HTHS) and one that provides fuel efficiency benefits while maintaining durability (lower HTHS). The proposal presented by the EMA includes performance specifications to address:
• Compatibility with and protection from biodiesel.
• Better engine protection from aeration.
• Better protection against scuffing wear.
• Improved shear stability and oxidation stability.
After receiving the request and conducting preliminary research, API determined that a need did indeed exist and eventually established the PC- 11 designation. In addition, the institute recognized the need to establish new category tests.
PC-11 will introduce two new oils: One will be increased engine protection at traditional viscosities, and the other will be new oils at lower viscosity which meet the same performance requirements. Two separate designations are sought for the two distinct specifications. PC-11 is scheduled for API licensing by Jan. 1, 2016.
Because current engines and components have undergone such a radical transformation in recent years, experts agree that the testing procedures for CJ-4 oils are quickly becoming obsolete. Telling is the fact that parts required to perform some tests will be scarce by 2015. Four new engine tests are in development for PC-11, including a new oxidation test. EMA is also considering an adhesive wear test to measure metal-to-metal contact.
“Current production HD engines are running hotter, and as a result more oxidation and nitration are being seen in the field,” Evans says. “EMA has requested that PC-11 contain a performance test based upon the current field hardware that can demonstrate oil performance differences in oxidation and nitration.” She adds that the Mack T-13 is the leading test candidate because it uses the new Mack MP8 engine hardware. Early testing has already shown that it is capable of increased oxidation severity compared to the Mack T-12 test that it’s intended to replace.
According to Evans, the T-12 test may continue as a ring and liner wear test for PC-11, and Detroit Diesel is working on a new test using the DD-13 engine platform to address adhesive wear of the piston and liner. “In all of these new test developments, it is imperative that they relate directly to real- world field performance,” she says.
Caterpillar is currently developing PC-11 test engine procedures and a test that measures oil aeration.
CATERPILLAR C-13 ENGINE OIL AERATION TEST
The test follows a procedure close to that used internally by Caterpillar for aeration engine testing. Similar to the development of any standardized engine test, they are working methodically with all the labs involved to define hardware and procedure details, develop initial tests to validate the concept and reach consensus between the labs. Caterpillar also has a task force that brings members interested in working on this development together for detailed technical discussions.
Hind Abi-Akar, technical expert, Fluids Engineering, for Caterpillar and a member of the EMA Lubricants Committee, says, “Thus far, the engine test has shown discrimination between high and low aeration oils. Hence, this portion has just the typical challenges of building a robust procedure that is representative to current engine technologies.”
The second aim of the aeration test is to develop a method of measuring the aeration of the oil that’s independent of the operator, more consistent and produces a population of data points. Currently the beaker or graduated cylinder method relies on the operator consistently drawing representative samples following the same process, and also on consistency in visually reading a meniscus of the oil and foam that tops it. Typical results are data points taken a few hours apart during the course of 30 hours of engine testing.
Abi-Akar says that noise in the resulting data is expected in the test. Caterpillar’s new aeration test relies on a micromotion technique to measure the air in the oil.4 The concentration of air in the oil is then calculated based on the density measurements. The result is an accurate and consistent reading of the aeration value in real-time and throughout the test duration. This technique eliminates operator error and produces data points throughout the test.
“We are conducting the graduated cylinder procedure along with the micromotion measurements to correlate the two since historically all the data available was obtained using the former method,” Abi- Akar explains. “We work together with all the labs involved and will employ statistical rigor to produce a test setup and procedure that satisfies ASTM standards and at the same time is more representative of current engines.”
She adds, “Our goal is a useful test that is current and representative and that can be supported for years. Since we have started this testing development early, we expect to meet or even be ahead of the timeline set by the NCDT for test development.”
FUEL ECONOMY TEST
There is not a test under consideration for fuel economy and there isn’t likely to be one in the future. Abi- Akar explains that measuring fuel economy for non-road engines is complex due to a broad variety of applications. “A wheel-loader has very different work cycles than a dozer or an excavator, for example,” she says. “How do you represent all this variation in a test? Potentially, the measure of fuel economy in off-road applications is unit-of-fuel-consumed per some unit-of-work-performed. We believe that measurements at the job site or overall project level will provide the most useful methods of improving off-road fuel economy. But due to this complexity, development of a standard test for fuel economy for off-road engines does not seem to fall within the oil category development activities at this time.”
Usually, when a new oil category is introduced, it is backward compatible to applications of existing categories. But things are not as clear cut with PC-11. Increasingly stringent regulations have created a generational divide between engines.
PC-11 may have to be split—EMA has recommended two API service categories. One subcategory would be a lower viscosity grade that has better fuel economy but with compromised protection in older engines (because of lower viscosity). This translates to very limited backward compatibility.
The other subcategory would be backward compatible—maintaining the performance of CJ-4 oils in higher viscosity grades such as 15W-40. This second subcategory would have the benefit of the additional oxidation stability, resistance to aeration, biodiesel compatibility, resistance to scuffing, and adhesive wear and increased shear stability but with little or no contribution to fuel economy.
Abi-Akar says that there was a consensus on the decision to request two categories. Caterpillar, as a heavy-duty, non-road machine and engine manufacturer, is focusing on the backward compatible category that preserves the current HTHS (high temperature/high shear) limits.
“The reason is that off-road engines typically have demanding loads and cycles and broad applications,” she says. “Engine durability and performance remain top priorities, and the oils have to be robust to ensure protection of these engines. We don’t anticipate that the low HTHS category will be applicable in older engines.”
She adds that low HTHS oils may not offer the level of durability due to the high loads experienced by non-road engines. In addition, engines experience boundary type conditions at their core moving parts under certain loads where the oil film thickness is critical to performance. Under boundary conditions, the fuel economy benefit of the low viscosity oils cannot be realized. So these oils would not improve the fuel economy of most heavy-duty applications.
ILSAC GF-6 is a new passenger car engine oil category proposed for licensing between June and September 2016. While the Diesel Engine Oil Advisory Panel develops new heavy-duty equipment categories such as PC-11, the new Auto-Oil Advisory Panel is the passenger vehicle counterpart. The Auto-Oil Advisory Panel, co-chaired by Teri Kowalski of Toyota and Luc Girard of Petro-Canada, replaces the ILSAC/ oil category development system— though it is comprised of basically the same people.
Like PC-11 the new category calls for improvements in fuel economy and better engine protection than currently exists at lower viscosities. For ILSAC GF-6, four needs were identified:
1. increased fuel economy. This needs to be maintained throughout the oil change interval.
2. enhanced oil robustness. This applies to spark-ignited internal combustion engines and is necessary to ensure acceptable engine oil performance in regional markets due to service requirements, fuel availability, environment issues, etc.
3. Protection against low-speed engine pre-ignition (LSPi). This specifically refers to LSPI attributed to engine oil.
4. Adequate wear protection for frequently started engines. These engines experience frequent starts and/or starts after extended periods of downtime.
ILSAC GF-6 TESTS
Evans explains that low-speed pre-ignition (LSPI) is a concern as it has been observed in the new generation of smaller-sized direct-injection turbopowered engines. Many automotive OEMs believe the occurrence of LSPI is related to fuel and lubricant properties. 6 Since the number of these direct-injection turbocharged engines will increase dramatically in the next few years, Evans says it is important that GF-6 has a meaningful test to screen for lubricant- and fuel-related LSPI events. But whether a GF-6 category should go forward without a test to measure the effects of LSPI on engine oil is currently being debated within the Auto-Oil Advisory Panel.
Chris Castanian, OEM liaison manager for Lubrizol in Wickliffe, Ohio, explains, “In severe cases, LSPI can damage pistons, degrade performance, lower fuel efficiency and increase emissions. Investigation is underway to determine the connection between engine oil and the LSPI phenomenon. Several OEMs have expressed interest in investigating and minimizing LSPI, leading ILSAC to include LSPI in the GF-6 needs statement. It would be a mistake to move the category forward without a performance-based engine test addressing LSPI in GDI engines, which are emerging as the leading light-duty gasoline engine technology in the world.”
A number of changes to test limits have been proposed by ILSAC. Five of these are as follows:
Sequence VH – sludge and Varnish formation
The Sequence VH will test an oil’s ability to prevent sludge and varnish formation. In an effort to improve deposit control and better protect against sludge and varnish, engine test limits will be tighter than the Sequence VG. As with the Sequence VG, the new test will reproduce the stop-and-go operating conditions of delivery vehicles and city driving in general. Ford will furnish a 2L turbocharged engine for the new test. Evans reports that the Sequence VH is being investigated for possible use to measure the effect of the lubricant on chain wear.
Sequence IVB – Wear
As with its predecessor, Sequence IVA, the Sequence IVB test will evaluate an oil’s ability to prevent wear in camshaft lobes by duplicating light city driving conditions. Wear requirements will be similar to Sequence IVA. This test will eliminate the Sequence IVA 1994 engine and replace it with an engine that better represents cars currently on the road.
Sequence IIIH – Viscosity and Piston Deposits
GM and Chrysler are both offering potential tests to replace the IIIG. Only one of them is expected to be included in the GF-6 final spec. The difference over the IIIG is that it will simulate highly loaded conditions, evaluating thickening resistance and piston deposit prevention under high-temperature conditions.
Sequence IIIGB—Phosphorus Volatility
The result of this effort was the introduction of a new phosphorus volatility test, the Sequence IIIGB, for ILSAC GF-5 that measures the percentage of phosphorus retained in the test lubricant during the Sequence IIIG test. In Europe there has been no activity to develop any industry standard test to look directly at the impact of the lubricant on any aspect of the after-treatment systems, including 3-way catalysts, NOx control devices or diesel particulate filters.
Sequence VID/VIe – Fuel Economy
The Sequence VID test measures the fuel economy contribution of engine oil. It is not scheduled to be replaced, only updated with higher fuel economy limits and perhaps renamed to Sequence VIE. The test engine will be a 2012 GM Malibu engine rather than the 2009 engine used in the current Sequence VID test. The GF-6 Needs Statement requested increased fuel economy performance standards for both new and aged oil.
In addition, ILSAC proposed two new engine tests for chain wear and aeration. A new bench test to measure low speed pre-ignition has also been proposed, but no test apparatus, procedure or limits have been as yet identified.
SAE will introduce a new viscosity grade for GF-6 (currently proposed as SAE 16), to its J300 specification. This viscosity grade has been established primarily for the fuel economy benefits of low-viscosity oils. Aeration remains a concern (ILSAC included an aeration test in its Draft Needs Statement for GF-6), but a test has not yet been proposed.
“For the tests measuring new parameters, the key to establishing a performance- based dynamometer test is to use oils with proven field issues and which demonstrate discrimination between good and bad performance,” Evans says. “For this reason, test development is always a difficult and time-consuming process.”
Castanian explains, “Lubrizol sees the necessity for engine oil specifications to address the substantive needs highlighted by the OEMs. Consequently, it would be appropriate to see tests for low speed pre-ignition, turbo deposits, chain wear and fuel economy durability included in ILSAC GF-6.”
With GF-6, two subcategories (one backward compatible and one not) are a given. The two subcategories will be called GF-6A and GF-6B.
GF-6A is the successor to GF-5 and will be backward compatible. It will include SAE 0W-20, SAE 0W-30, SAE 5W-20, SAE 5W-30 and SAE 10W-30 oils. The minimum high-temperature/ high-shear viscosity for all GF-6A grades will be 2.6 mPa-sec.
GF-6B is a subcategory meant for the SAE 0W-16 and SAE 5W-16 viscosity now being developed. They will not be backward compatible. GF-6B may have the same performance requirements as GF-6A except for a high-temperature/high-shear viscosity of less than 2.6 mPa-sec. As with PC- 11, the viscosity of GF-6B may be too low for older engines.
It’s apparent that from now on engines and lubricants (and, in some cases, fuels) will need to be developed simultaneously with an eye toward optimal fuel economy and energy usage for the entire system. Although this side-by-side development is relatively new, the effects on quality are already apparent. In 2012 the average age of passenger cars and light-duty trucks on the road in the U.S. was at a record high 10.8 years.7 PC-11 and GF-6 are expected to continue prolonging engine life and improving performance.
“The current environment is particularly challenging, with both ILSAC GF-6 and PC-11 test development efforts vying for the limited resources available to complete these tasks successfully,” Evans says. “The challenge is compounded further by the stated desire to keep the timelines for the two developments separated by at least a year.”
Abi-Akar notes the importance of labeling. “Market confusion is a concern,” she says. “We hope that endusers are not confused with the presence of two new categories and we are working through the API process to ensure that the labeling of the two categories is unambiguous to customers and end-users. The latter is critical. This can be another challenge for customers wishing to use the two categories— to use each where appropriate. The engine manufacturer recommendation has to be closely followed.”
Jean Van Rensselar heads her own communications/public relations firm, Smart PR Communications, in Naperville, IL. You can reach her at firstname.lastname@example.org
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