API SQ category advances amid debate over sulphated ash limits

The new API Service Category SQ (API SQ) was announced at the June 2024 meeting of the API Lubricants Group. Shortly thereafter, a draft table outlining API SQ was sent for review and comment. Since then, the API Lubricants Group has been working to finalise the API SQ specification table, with a target first license date of March 31, 2025. 

The API “S” Service Categories define performance standards for motor oils used in gasoline engines. API SQ will build on the performance benefits of API SP, by introducing enhanced protection to meet the evolving needs of modern engines designed to meet stringent fuel economy and emissions requirements.

Typically, API “S” Categories closely align with the International Lubricants Standardization and Advisory Committee (ILSAC) engine oil performance standards. API SQ will align with ILSAC GF-7 and include additional considerations for non-ILSAC viscosity grades including the new ultra-low viscosity oils, SAE 0W-8 and SAE 0W-12. 

ILSAC GF-7, which was approved by the Auto Oil Advisory Panel (AOAP) in May 2024, included the ASTM D874 Sulphated Ash Content (SASH) with a 0.9% maximum limit. SASH is a byproduct when engine oil containing detergents and anti-wear additives are consumed in the engine. The ash can accumulate in the exhaust emission control system such as the Gasoline Particulate Filter (GPF), clogging its passages and resulting in a loss of engine performance. Lower SASH engine oils help ensure the proper functioning and long-term health of emissions control systems and reduce the need for costly repairs and maintenance and system life. 

At a Lubricants Group meeting on August 29, members had their first opportunity to offer corrections and comments on the draft API SQ Service Category table. API SQ updates API SP performance, including changes to the Sequence IIIH engine test, which measures high-temperature viscosity increase and deposits; the Sequence VH engine test, which assesses lubricant performance in controlling low-temperature engine deposits; and the Sequence VI, which evaluates the comparative fuel economy of automotive engine oils. Additionally, API SQ addressed new oil mini-rotary viscosity (MRV) limit; Engine Oil Gelation (rate and report); and Elastomer Compatibility aligned with ILSAC GF-7. Also, the API SQ “Chemical Box” (Sulphur, Phosphorus, SASH) expanded to include SASH. For API SQ, the SASH Limit was initially proposed for all viscosities and classifications.

This is the first time SASH has been incorporated into the “Chemical Box” in the “S” Category. In the past, API standards have focused primarily on phosphorus and sulphur levels to protect emission control systems. Controlling the level of SASH in engine oil is crucial for protecting Gasoline Particulate Filters (GPF), a key component in modern emission control systems.

ILSAC GF-7, which was approved by the Auto Oil Advisory Panel (AOAP) in May 2024 included a SASH requirement, ASTM D874 Sulphated Ash Content of 0.9% maximum. 

On September 17, the Lubricants Group met a second time to discuss reaching a consensus on API SQ specifications. Most corrections, changes and proposals were reviewed and addressed with a modest amount of discussion. One of the more discussed topics was the addition of a SASH requirement which was only for oils classified as API SQ with Resource Conserving (i.e., ILSAC viscosity grades). 

Mike Deegan, ILSAC chair and a representative of Ford Motor Company, emphasised ILSAC’s preference for consistency in SASH limits with ILSAC standards, noting concerns about potential confusion in the North American market. He also noted that limiting ash levels helps meet government-imposed minimum emissions control system life requirements.

In contrast, lubricant manufacturers argue that SASH limits are unnecessary for non-ILSAC viscosity grades. API SQ must accommodate a wide variety of formulation styles where higher ash levels are necessary, says Dan Pridemore, industry liaison manager, Americas, from Infineum. Submitting that it is only appropriate to include the SASH limit in the API SQ Resource Conserving category, to ensure compatibility with GPF emissions systems.

Mike Alessi, technology integration manager – advocacy, at ExxonMobil suggested that performance improvements with API SQ are not dependent on the SASH limit, as demonstrated by existing products with higher SASH levels that meet API SP standards. He stressed that a 0.9% SASH maximum for non-resource-conserving engines could impact certain end users based on existing approvals and specifications.

Mike Warholic of Valvoline Global Operations argued that non-ILSAC viscosity grades should have no SASH limits due to the presence of high ash products in Europe. Valvoline believes this would be beneficial for API licensing in different regions, contributing to a globally applicable standard.

Afton Chemical’s Director of the Americas OEM Relationship Team, Brent Calcut, highlighted a precedent for treating grades differently. A 0.9wt% for ILSAC grades, but with the exclusion of non-ILSAC grades, would align with the lack of a phosphorus maximum for other eligible viscosity grades under API SP, the current API S category. It was noted that the majority (about 90%) of current licenses for API SP are resource-conserving, with the remaining covering a variety of applications such as motorcycles and heavy-duty. 

The discussion was not reaching a consensus. As a result, Darryl Purificati, chair of the API Lubricants Group and senior technical advisor at HF Sinclair, made a motion to ballot the inclusion of a SASH limit for only API SQ with Resource Conserving, with a maximum SASH limit of 0.9%. The intention of the ballot was to gather in-depth comments and feedback from stakeholders and their companies to guide additional discussions. The motion was seconded by Eric Kalberer, global product application specialist and industry liaison at Shell. The motion was passed unanimously by the 14  members in physical attendance at the meeting. The 30-day ballot on the issue of SASH was issued on September 20.

It is anticipated that ballot adjudication will be addressed at the next Lubricants Group meeting or at the December Lubricants Group meeting to be held in conjunction with the ASTM D02 meeting in Anaheim, California, U.S.A.