What is PC-12?

Heavy duty diesel engine oils will be undergoing a category upgrade in the coming years. The Proposed Category 12 (PC-12) engine oils are in development now and will be licensed for use in early 2027. We are here to help you navigate the change and provide perspective about the important pieces of information you should be aware of with this category upgrade and what this means for your engine.

OEM Technical Services Manager, Shell, Karin Haumann is chairperson of the API New Category Development Team (NCDT) leading the innovation of engine oils to meet industry needs. The API NCDT is committed to continuously providing customers with . Over the next several years, we will update this page with new content to share information, help address concerns and ensure that the transition into PC-12 is smooth.

What is PC-12?

In December 2022 the US Environmental Protection Agency (EPA) released a new rule that requires engine manufacturers to meet more stringent emissions standards. These regulations will come into effect in Model Year 2027 engines. While it is still three years away, engine manufacturers are working hard on technology to meet the new standards. The new standards are another step change in reducing emissions from heavy duty diesel engines, and include a 75% reduction on Nitrous Oxide (NOx) emissions, and a 50% reduction in Particulate Matter (PM). The EPA are also phasing in stricter greenhouse gas emission standards, and placing more emphasis on service life of components. Aftertreatment systems (such as AdBlue systems, diesel exhaust fluid (DEF), and diesel particulate filters (DPF)) must achieve a longer service life. In the USA this will extend out from around 435,000 miles (700,000 km) to 800,000 miles (1,290,000 km).

All of these changes will mean that the heavy duty diesel engine oil will also need to change to help keep engines operating as their manufacturers intended. To that end, engine manufacturers made a request for a new engine oil category to facilitate the changes needed to meet the new regulations. This is called Proposed Category 12 (PC-12). PC-12 was formally endorsed by the American Petroleum Institute (API) in early 2022, and in the future this will become the most modern oil standard. Right now, the new category is being called PC-12 (or proposed category 12), to be split into two parts PC-12a and PC-12b.

The current engine oil categories, API CK-4 and API FA-4 were introduced in 2016. CK-4 was intended to cover engines manufactured around the 2016 timeframe and was backwards compatible with older engine technology, while the FA-4 standard was designed to ‘future-proof’ the oil category, to help protect more fuel efficient engines that were on the horizon at the time. That has played out in the market as OEMs search for better fuel economy, more power and longer oil drain intervals. Similar to PC- 11 facilitating hardware improvements in 2016, PC-12 will enable further advancements in engine technology.

Why is there a need for a new engine oil category?

Government mandates from the US Environmental Protection Agency (EPA) and California Air Resources Board (CARB) are putting new regulations on heavy-duty engines. In response, heavy duty engine oils will also evolve, to ensure that lubricants continue to meet performance expectations for both old and new engines.

Oil technology and engine technology go hand in hand. Changing regulatory limits challenge engine manufacturers to reduce emissions. As engine manufacturers begin to create a new generation of cleaner, more fuel-efficient diesel engines, they need a new generation of higher-performing diesel engine oils to protect them.

OEM’s look at a wide range of technologies to help an engine achieve lower emissions targets, and one key way to do this is to use a lower viscosity engine oil which burns less fuel. Lower viscosity engine oils mean less internal friction, meaning the engine expends less energy on internal friction, leaving more energy available to drive the truck wheels.

We have seen reduced viscosities under the API FA-4 standard, where 5W-30 and 10W-30 oils are now common. Under the new PC-12 category, OEM’s are coming to oil manufacturers asking to provide even lower viscosity formulations.

What are the expected benefits of the spec upgrade?

• Greater Heat Tolerance/Oil Drain Interval (ODI) Extension
  • Better Oxidation Performance enables possible increase in fuel economy OR possible increase in ODI
• New Wear Test Ensuring Wear Protection
  • Ensures wear protection of low viscosity oils and protection against liner scuffing
• Improved Aftertreatment Performance
  • New chemical limits can extend service intervals and service life
• Lower Viscosity = Improved Fuel Economy
  • Low viscosity directly enables fuel economy/ Greenhouse Gas (GHG) reduction

What is the timing of PC-12?

The anticipated first licensing date for PC-12 is January 1, 2027. PC-12 will align with the introduction of the model year 2027 engines.

What do I need to know now?

The first licensing date for PC-12 remains early 2027.

• The PC-12a subcategory will continue to be backwards compatible, just like CK-4 is today.

• A new chemical window (chemical limits for the HDEO formulations) has been agreed by the PC-12 committee

• Phosphorous limits will be reduced as part of the new category

• Ash and sulfur limits are also dropping

• The primary benefits of these changes is:
  • Greater Heat Tolerance/ODI Extension
    Better Oxidation Performance enables increases in fuel economy through higher operating temperatures OR possible increase in ODI
  • New Wear Test
    Ensuring Wear Protection Ensures wear protection of low viscosity oils and protection against scuffing
  • Improved Aftertreatment Performance
    New chemical limits can extend service intervals and service life
  • Lower Viscosity = Improved Fuel Economy
    Low viscosity directly enables fuel economy/ Greenhouse Gas (GHG) reduction

• Future proofing the category with the addition of lower oil viscosities to include xW-20 in the F subcategory

DEVELOPING NEW DIESEL OIL PERFORMANCE STANDARDS

API Service Category Development Phases