As new regulations introduce significant emissions reductions for Model Year 2027 over-the-road commercial vehicles, the industry continues to move forward with developing the new PC-12 heavy-duty engine oil category. These vehicles will require significant updates to both engine hardware and after-treatment systems to meet the latest emissions regulations. The PC-12 oil category is being designed to ensure that heavy-duty engine oils continue to deliver protection to these systems while supporting improved fuel efficiency and environmental performance.
The origin of PC-12
With a global push for cleaner air and decarbonization, North America’s Environmental Protection Agency (EPA) and California Air Resources Board (CARB) are introducing more stringent emissions regulations. By 2027, the EPA’s Clean Trucks Plan will aim to reduce nitrogen oxide (NO) emissions by more than 80%. This drastic reduction will require significant upgrades to heavy-duty diesel vehicles, including more advanced after-treatment systems designed to meet these new limits. As a result, CARB is implementing ultra-low NOx limits, further challenging OEMs to adapt.
These strict emissions standards, along with the push for better fuel economy, have led the Truck and Engine Manufacturers Association (EMA) to request the development of a new oil category: PC-12. The goal of this new category is to ensure that lubricants continue to protect engine hardware while supporting the lower viscosity oils needed for improved fuel efficiency.
Key category updates
PC-12 will introduce several changes:
- Tighter chemical limits: New limits for phosphorus, sulfur, and sulfated ash are being introduced to protect advanced aftertreatment systems.
- Lower viscosity grades: The introduction of lower viscosity grades (SAE XW-20) is intended to enhance fuel economy and reduce greenhouse gas (GHG) emissions while providing the needed oxidation performance and wear protection.
- Hydrogenated nitrile seals: New seals made from hydrogenated nitrile butadiene rubber (HNBR) have been introduced for additional protection, though proposed limits are still pending.
- Two PC-12 categories:
- PC-12A: Expected to be backward compatible with prior API “C” specifications.
- PC-12B: This category may have different viscosity and soot control requirements, potentially affecting its backward compatibility with the current FA-4 category.
- Testing and progress: New tests are being developed to address this the Detroit DD13 scuffing test and the Cummins ISB viscosity test, which address concerns around scuffing and soot handling in lower viscosity oils. Test development and refinement are progressing, with matrices for base oil interchange and viscosity grade to be finalized by the end of 2024.
- Reference oils: Testing of new reference oils is underway, including the Cummins ISB wear reference oil and Volvo T-13 reference oil, with some challenges regarding oil consumption still being addressed. These are essential benchmarks used in industry testing to ensure consistent performance and compatibility with new engine designs.
- Timeline: PC-12 is on track for the proposed First License date of January 1, 2027.
New engine oil specifications
With the significant advancements expected in MY 2027 heavy-duty diesel engine, the PC-12 oil specification is being designed to provide the protection these new systems will demand. The new oil specification will focus on:
- Improved oxidation protection.
- New wear tests for better engine longevity.
- Lower viscosity grades to improve fuel economy.
- Aftertreatment durability to support new vehicle technologies.
- Enhanced elastomer compatibility for seals and gaskets.
- The removal of obsolete tests and the introduction of new tests to meet evolving requirements.
The importance of switching to low-viscosity engine oils
As the PC-12 specification evolves, one of the most significant changes is the shift to lower-viscosity engine oils. This change is driven by the industry’s broader goal of improving fuel efficiency and reducing emissions, which aligns with the push for more sustainable and cost-effective engine operations.
Switching to low-viscosity, heavy-duty engine oils is crucial in this transition. The new oils, which offer improved oxidation and reduced fuel consumption, are not only key to meeting emissions targets but also deliver significant benefits for both older and newer engine designs. The move towards lower viscosity grades – such as the shift from 15W-40 to 10W-30 – promises meaningful fuel savings, improved engine durability and enhanced protection, making it a vital component of the ongoing efforts to enhance engine performance and lower emissions.
A balanced formula of calcium and magnesium may be the answer to lowering emissions and enhanced engine performance
Premium API CK-4 heavy-duty engine oils like CITGO® CITGARD® 700 Synthetic Blend Heavy Duty Engine Oil SAE 10W-30 utilize a balanced approach to protect your engine and maintain your Diesel Particulate Filter (DPF) life.
What sets this oil apart is its unique balanced detergent additive package (roughly equal amounts of Calcium and Magnesium detergents) versus many competitors that have Calcium-only detergent packages. Magnesium ash tends to be more porous and less dense than Calcium ash, which produces the following benefits:
- Reduced exhaust flow resistance
- Reduced back pressure (50%)
- Less workload on engine
- Improved fuel efficiency
The CITGARD 700 Synthetic blend 10W-30 detergent package also helps maintain engine cleanliness, protects the engine, and maintains DPF life through excellent oxidation control.
PC-12: looking ahead
As the industry faces mounting pressure to reduce emissions, the development of the PC-12 category is an important step in ensuring that heavy-duty engine oils keep pace with these changes. The new specification will address the need for improved fuel efficiency, improved engine durability and more effective aftertreatment system protection, all while supporting the transition to cleaner, more efficient vehicles and reduced emissions footprint.
Contact your supplier about choosing the right balanced formula in heavy-duty engine oils, such as CITGO’s premium line of CITGARD HDEOs, for your fleet operation and emissions compliance. The right HDEO could also help you streamline and simplify your inventory planning and supply needs.
