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PC-12 FAQs: Preparing for the Next Generation of Engine Oil Standards
As the heavy-duty engine oil industry prepares for the next wave of regulatory and performance demands, the proposed PC-12 category emerges as a pivotal evolution from the current API CK-4 and FA-4 (PC-11) specifications. Designed to support the stringent requirements of 2027 on-highway diesel engine regulations—including reduced NOx and CO₂ emissions and extended aftertreatment system life—PC-12 introduces two subcategories: PC-12A (C-category) and PC-12B (F-category).
The following FAQs provide a comprehensive overview of PC-12, detailing the drivers behind the change, key specification updates, chemical composition considerations, and implications for current formulations and licensing. Whether you're an oil marketer, OEM, or industry stakeholder, this guide will help you navigate the transition and prepare for the future of heavy-duty engine oils.
1. What is PC-12?
PC-12 is the new API “proposed category” to upgrade the current API CK-4 and FA-4 (PC-11) categories. Much like PC-11, PC-12 will have 2 subcategories: PC-12A (C-category) and PC-12B (F-category). The industry is proactively defining the performance requirements for the next generation of heavy-duty engine oils.
2. What is driving the change?
To meet new regulations for on-highway diesel engines set for 2027, which include lowering NOx emissions, extending the life of the emission equipment, and reducing CO2 emissions, equipment manufacturers require a new specification to meet these challenging regulatory requirements.
3. Why change the specification?
With the changes to the specification, the objective is to improve engine reliability, ATS compatibility, and drive efficiency. It is essential for heavy-duty engine oil lubricants to continually improve in terms of quality and performance, looking beyond today’s performance requirements.
4. At a high level, what is changing?
PC-12A is maintaining historical HDEO viscosity limits and planned backward compatibility with historical C-categories; however, we anticipate the introduction of lower HTHS viscosities for the API “F” category (PC-12B) where read-across and backward compatibility may be limited.
5. What is the difference between PC-12A and PC-12B?
The primary difference between PC-12A and PC-12B is high temperature, high shear requirements (HTHS). This requirement will differ slightly from the PC-12B equivalent category today, API FA-4.
HTHS comparison to PC-11 limits and limit changes for PC-12B:
| Parameter | API CK-4 PC-11 | API FA-4 PC-11 | API “C” PC-12A | API “F” PC-12B |
| HTHS | ≥ 3.5 | 2.9-3.2 | ≥ 3.5 | 2.6-3.2 |
6. What is the PC-12 chemical box (SAPS)?
The chemical box or SAPS (sulfated ash, phosphorus, and sulfur) referenced in PC-12 is not chemically different than the chemical box in previous categories. However, emphasis on aftertreatment system compatibility, SAPS limits (chemical content), is expected to change. Some OEMs are also exploring limiting the content of Na and K in addition to SAPS limits.
Proposed SAPS limit changes compared to API CK-4 (PC-11):
Parameter | API CK-4 | API “C” |
Sulfated Ash | 1 wt.% max | 0.9 wt.% max |
Phosphorus | 0.12 wt% max | 0.08 wt.% max |
Sulfur | 0.4 wt.% max | 0.3 wt.% max |
7. What are the key specification limit changes from API CK-4 to PC-12?
While most of the engine tests remain the same, there are 3 key changes being introduced with PC-12:
- Stringent T-13 oxidation requirements for infrared abs and viscosity change
- T-11 replacement by a newly introduced ISB-Viscosity test
- New sulfated ash, phosphorus, and sulfur (SAPS) limits are being introduced
See table below for improvement areas and anticipated changes with PC-12, along with a comparison of PC-11 limits. Note that limits are not final and are subject to change based on industry guidelines.
| Test | Improvement or Change | API CK-4 PC-11 | API “C” PC-12A | API “F” PC-12B |
| Volvo T13 | Oxidation | IR ≤125 abs; ∆KV≤75% | IR≤80 abs; ∆KV≤50% | IR≤80 abs; ∆KV≤50% |
| T11 replacement | ISB-Viscosity | ≥ 6.7% soot @15cSt vis increase | ≥6.7% soot @15cSt vis increase | 12cSt max vis inc. at 4.8% soot |
| Sulfated Ash | DPF compatibility | 1% wt% max | 0.9wt% max | 0.9wt% max |
| Phosphorus | ATS compatibility | 0.12% max | 0.08% max | 0.08% max |
| Sulfur | ATS compatibility | 0.4% max | 0.3% max | 0.3% max |
8. What about backwards compatibility?
The PC-12A or C-category specification is expected to maintain historical HDEO viscosity limits and backwards compatibility.
9. What will happen to the current API CK-4 category, and will it become obsolete?
API CK-4 and PC-12 will coexist in the market. It is anticipated that API CK-4 will remain an active, licensable API category; there are no current industry plans to make it obsolete.
10. How will this affect my current CK-4 Heavy Duty Engine Oil formulations, and will my formulations need to be adjusted?
We anticipate that finished fluid formulations for PC-12 will change to meet new requirements. However, the transition timing from API CK-4 to PC-12 will be defined by the oil marketer and their timeline. Afton’s approach to PC-12 is to provide the most flexibility and comprehensive base oil coverage, meeting the evolving needs of the market and its customers.
11. Is the API licensing and approval process changing?
The API licensing process is not anticipated to change; however, the OEM approval process is subject to change based on OEM requirements and internal processes. Should there be any changes to the licensing and approval process, this will be communicated to the industry.
12. What is the timing?
PC-12A and PC-12B are anticipated to become a licensable API category on January 1, 2027. If you would like to learn how Afton can help meet your heavy-duty engine oil needs beyond current requirements, please contact us.