Consumers do not see the army of professionals involved in this work, from the OEMs who dictate the need, to the marketers that blend and distribute products. In between are the additive companies that develop the technology, the test labs used to qualify products and many organizations that support the activities, including the American Petroleum Institute, ASTM, the European Association of Automobile Manufacturers (ACEA), the Technical Association of the European Lubricants Industry (ATIEL), the American Chemistry Council, the Test Monitoring Center and SAE to name just some! These groups take great pride in ensuring the market can protect your brand new 2025 gasoline or diesel engine as well as a 50-year-old tractor or vintage Corvette.

So, what are the issues, and how does industry ensure lubricants are back serviceable, also referred to as backward compatible? Is there a path to maintaining an older specification for oils that are still required around the globe? Can a new product still protect your older engines. We should remember that some markets differ significantly. For example, North America prefers that the new product is fully backward compatible and protects all older engines, while other markets are more fragmented and continue to use products that were formulated for older specifications. Also, due to the drive toward improved fuel economy and lower viscosity and the development of
new viscosity grades, back serviceability is not always possible for certain viscosity grades. Some specifications are mutually exclusive due to a chemical limitation that was added for newer fluids.  

Specifications are designed around a series of engine and bench tests, and it is critical that these tools be maintained. While most bench tests can be maintained and do not change much over time, engine hardware and controls continue to evolve, and so have the fuels to run these tests. Like other older technologies that are no longer used, older engine tests must be retired when parts and engines run out and therefore can no longer be supported by industry stakeholders.

Afton Chemical’s Brent Calcut chairs the group dedicated to enabling older API specifications to live on — a task gaining increased attention.

“API’s Category Life Oversight Group was formed during ILSAC GF-6 development, when industry was introducing four different replacement engine tests while developing the new category,” he said. “CLOG’s task was to focus on looking backwards to maintain existing API S and C categories while AOAP [the Auto-Oil Advisory Panel] was more focused on looking ahead to develop GF-6.

“CLOG is important today for similar reasons. API C categories are facing the end of life of three tests, the Mack T-8, T-11 and T-12. Identifying potential replacement tests and then eventually collecting sufficient data to develop equivalency limits is not trivial. CLOG is again focused on looking backward to maintain existing API categories while NCDT [the New Category Development Team] maintains focus on developing the new [API] PC-12 category. CLOG’s work will be required to maintain all API C categories from [API] CH-4 up to the latest CK-4 and FA-4.”

It should be noted that maintaining older specifications became a priority when the late Thom Smith, of Valvoline, served as chairman of CLOG last decade. At that time changes in hardware and evolution of viscosity grade presented new challenges to efforts to maintain older tests. For example, we can look at the Sequence III test for oxidation and deposits — one  of the most critical and formulation-defining tests. For ILSAC GF-1, we started out with Sequence IIIE on leaded fuel but today use the Sequence IIIH with unleaded fuel, having passed in between through the Sequence IIIF and the Sequence IIIG. Wear tests, that were once covered by the Sequence VE and the Sequence IIIG were replaced by the Sequence IVA, and for GF-6 the Sequence IVB.

For licensing purposes, API SH and its companion specification ILSAC GF-1 are no longer licensable. API SJ and is still licensable for light-duty engines, thanks to lengthy industry efforts. API SJ covers 2001 and older vehicles and has been covered by subsequent categories including ILSAC GF-7 (API SQ), which was introduced this year.  

Another key performance criteria concerns “soot-induced viscosity increase.” Once upon a time this was defined by the Mack T-7 test, which was part of API CE and CF-4. Historically Mack provided this test along with several subsequent versions. Volvo, which owns Mack today, has limited its participation in developing new tests and stopped supporting PC-12 programs, while Cummins stepped in to help.

“CLOG is immediately focused on developing equivalency limits for the Mack T-8 and T-11 in the new Cummins ISB Viscosity Test,” Callcutt said. “These tests are incorporated into every existing API C and F category as well as every ACEA E Sequence and many OEM specifications as well. There are four different sets of limits within the API categories where CLOG is expected to recommend equivalency, plus the ACEA limits, which are slightly different. While CLOG is specifically tasked with developing equivalency limits for API categories, the outcome will be considered for ACEA and OEM specifications.”

Calcut talked about the key tools used to decide when to preserve an old test and when to develop a replacement.

 “Ideally, there’s an obvious replacement test available, such as the Cummins ISB-V Test replacing the Mack T-11,” he said. “In this case, we will have precision matrix results, whereas typically at least one reference oil from the original test was included. If there are no relevant precision matrix results or CLOG desires more data, there are a couple additional options. One, ask ACC if member companies have data they are willing to anonymously collect and share with the industry; or two, design a small test matrix and request funding from industry sources.

“For the Mack T-11 replacement we have a combination of data from the precision matrix, and ACC donated data for analysis. Industry statisticians are extremely valuable resources for determining how best to analyze the data to determine equivalency.”

It should be noted that soot-induced viscosity tests represent a key formulation defining test for diesel engine oils today and going all the way back to the 1980’s — which is the limit to my memory. Old tests such as the Mack T-6, T-7 and NTC 400 were replaced with more modern hardware that OEMs were confident would manage older equipment.

Categories like API CE, API CF-4 and API CG-4 became obsolete from an API standpoint as they did not have appropriate tests defined to meet those specifications. But industry still maintains API CH-4 , which was introduced in 1998, along with newer categories, and it is critical that Industry develops equivalency for the new Cummins test for these widely used products.

The latest heavy-duty diesel oil specification, API CK-4, which will soon be upgraded to PC-12, but outside North America consumers primarily still use API CH-4 or CI-4, and these represent most of the commercial volume globally. These quality levels are critical for many markets. It is also true that API CF-4 did not go away when API declared it obsolete, and some regions still demand this quality level. While OEMs and marketers alike might want all consumers to upgrade to more current lubricants, there is still a demand from fleets and users that do not want to pay more for newer oils.

With no mandates to use particular specifications, end users must rely on the technical judgement of their favorite suppliers to decide what specification to use, and that brings us to what was once described to me as the wild, wild West of engine formulation. One thing that helps allow newer formulations to work well in older engines is that fuel and specifically fuel sulfur levels have been greatly reduced everywhere in the world, reducing the level of TBN needed to neutralize acids.

Industry should make sure that PC-12 is back serviceable to current and past categories as there are many diesel engines on the road for which older specifications were recommended — both in North America and the rest of the world. While North America may like a one-size-fits-all product, that is clearly not the case in all regions. Even in North America new lower-viscosity products will not be back serviceable. API FA-4 was a forward-looking category and the upcoming API FB-4 may not be back serviceable to API FA-4 since it will allow SAE XW-20 engine oils, in contrast with FA-4, where SAE XW-30 is still the lightest vis grade.

 Calcut said a priority for PC-12 is to replace the Mack T-12 test, but that it may take two methods to do so.

“After addressing Mack T-8 and T-11 equivalency, CLOG will turn its attention to the Mack T-12,” he said. “This task is expected to be significantly more challenging since we are lacking an obvious direct replacement test. The Mack T-12 measures two distinctly different oil properties — ring and liner wear as well as compatibility with lead bearings, which is often compromised by oil oxidation. There are no replacements for consideration that measure both wear and bearing compatibility, so these performance attributes will likely have separate recommendations.” 

At the end of the day, the goal is to assure consumers around the world that there will licensed oils — meeting new or old specifications — to protect their expensive engine. 

Steve Haffner is president of SGH Consulting LLC. He has over 40 years of experience in the chemical industry, primarily with Exxon Chemicals Paramins and Infineum USA. Contact him at sghaffn2015@gmail.com or 908-672-8012.