New pc-11 diesel motor oil specification is required for the latest engine design.

A new pc-11 diesel motor oil specification is being developed to cope with recent changes to environmental regulations and engines. 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 the new GF-6 motor oil specification for passenger automobiles.

For the first time each specification will have two versions: one for current and future engines and another compatible with older engines. Although
consumers will need to exercise more caution when selecting engine lubricant, engines of all ages will greatly benefit.

Introduction to the new pc-11 diesel motor oil specification.

In 2011 the National Highway Traffic Safety Administration (NHTSA) issued a regulation, limiting greenhouse gases and forcing an improvement in fuel consumption for medium and heavy-duty trucks. Phased in from 2013 to 2018, this is the 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. The new pc-11 diesel motor oil specification (PC stands for proposed category) will offer performance beyond API CJ-4 engine oils.



The API CJ-4 oil specs, introduced in October 2006, has been the standard for quite a while, 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 new pc-11 diesel motor oil specification 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 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. 
• Reduced aeration susceptibility.
• Better protection against scuffing. 
• Improved shear and oxidation stability. 

The new pc-11 diesel motor oil specification will cover two new oils: One with increased engine protection at traditional viscosities, and the other for new oils at lower viscosity which meet the same performance requirements. While two separate designations are sought for the two distinct specifications. The introduction of PC-11 is scheduled for API licensing by Jan. 1, 2016

The new pc-11 diesel motor oil specification brings new testing regime.

Because of the radical development of diesel engines in recent years, engineers decided that the testing procedures for CJ-4 oils needed overhauling. Four new engine tests are being considered for introduction with the new pc-11 diesel motor oil specification, 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 diesel engine oils are experiencing elevated levels of oxidation and nitration in the field. As a result EMA has requested that the PC-11 contains a performance test based upon the current field hardware that can demonstrate oil performance differences in oxidation and nitration. The Mack T-13 is the most likeley 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.

Nevertheless, the T-12 test may continue as a ring and liner wear test for the new pc-11 diesel motor oil specification, whilst at the same time Detroit Diesel is working on a new test using the DD-13 engine platform to address adhesive wear of the piston and liner.

To further enhance the real world simulation, Caterpillar is currently developing a PC-11 test engine test procedure that measures oil aeration.

The new pc-11 diesel motor oil specification uses the Caterpillar C-13 engine oil aeration test.

The test is similar to that used internally by Caterpillar to test for aeration of engine lubricant. As with 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.

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 has the typical challenges of building a robust procedure that is representative to current engine technologies.”

The second objective of the aeration test is to develop a method of measuring the aeration of the oil independent of the operator, that’s 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.

The new Caterpillar aeration test relies on a micromotion technique to measure the air in the oil. The concentration of air in the oil is then calculated based on 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 reliable data points throughout the test.

The goal is a useful test to support the new pc-11 diesel motor oil specification that is current and representative and that can be used for years to come. As development of the test procedure is well advanced a finalised document should be available ahead of the timeline set by the NCDT for test development.

No fuel economy test for the new pc-11 diesel motor oil specification.

No test is under consideration for fuel economy and there isn’t likely to be one in the future as measuring fuel economy for non-road engines is complex due to the broad variety of applications: A wheel-loader has very different work cycles compared to a Dozer or an excavator.

Potentially, the measure of fuel economy in off-road applications is unit-of-fuel-consumed per some unit-of-work-performed. The measurements at the job site or overall project level are likely to provide the most useful methods of improving off-road fuel economy. But due to the 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.

Two subcategories of the new pc-11 diesel motor oil specification.

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 the new pc-11 diesel motor oil specification. Increasingly stringent regulations have created a generational divide between engines.

Because of this, 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.

Caterpillar by way of example, as a heavy-duty, non-road machine and engine manufacturer, is focusing on the backward compatible category of the new pc-11 diesel motor oil specification 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, and therefore engine durability and performance remain top priorities, and the oils have to be robust to ensure protection of these engines. They don’t anticipate that the low HTHS category will be applicable in older engines.”

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.

The new pc-11 diesel motor oil specification going forward.

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.

The current environment is particularly challenging, with both ILSAC GF-6 and the new pc-11 diesel motor oil specification test development efforts vying for the limited resources available to complete these tasks successfully. The challenge is compounded further by the stated desire to keep the timelines for the two developments separated by at least a year.

While the world waits the finalisation of the new pc-11 diesel motor oil specification for diesel engine lubricant you can rely on the quality synthetic engine oils supplied by Habot Oil. Call au for a consultation, to find out what these fully synthetic oils can do for you.