Proposed Category 11 (PC-11): What It Means for the Heavy Highway Industry


semi driving in mountains oil category change | Highway & Heavy Parts


Until now, oil changes have been rather routine maintenance procedures for diesel engine fleet owners, but with new Greenhouse Gas (GHG) emission regulations being implemented by the National Highway Traffic Safety Association (NHTSA), the days of simply dumping a few gallons of 15w40 into an engine could soon be a thing of the past. 

These more stringent regulations have resulted in the development of a new commercial engine oil performance category known as Proposed Category 11 (PC-11). Unlike previously created performance categories that aimed to improve engine durability and meet the needs of technologies used to reduce exhaust emissions, PC-11 was created largely to reduce GHG emissions and improve fuel economy.


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What is PC-11?

In order to address the issue of fuel economy, two new blends were in the works in the category to meet federal regulations for heavy trucks being phased in between the years 2014 and 2018.

Many experts believe that eventually this could result in owners and end users having to carry not one but two grades of oil in order to fully cover the different trucks in their fleet. This includes the already popular heavier viscosity oils such as SAE 15w40, along with newer, low-viscosity, fuel-efficient mixtures.

The creation of these two new subcategories further complicates matters due to the fact that it's unlikely that the low viscosity oils will be compatible with legacy engines.

Although low viscosity oils offer greater fuel economy, they provide significantly less wear protection. As a result, many older diesel engines that utilize these grades will be less protected from the normal wear and tear that typically occurs over the lifespan of a truck. The increased use of trucks fueled by liquefied natural gas (LNG) may further complicate issues due to the fact that they require specially manufactured oils to meet the operating temperature requirements of their engines.  

Want to know more about when you should be changing your oil? Read our post on oil change intervals after break-in!


How does this affect my diesel engine?

If you're wondering how these changes will affect you and your diesel engine, you're not alone. Emission requirements have caused many changes in the diesel engine industry already, and that's not likely to stop any time soon. 

Though many experts believe that there will be a continued push towards low viscosity fuels that result in greater fuel economy and less CO2 emissions, they also believe that many of the heavy, high viscosity oils used today will remain prominent for both on-highway and off-highway purposes.

And as fleet owners continue to look for new and innovative ways to cut operating costs and maximize uptime, the development of lubricants that can adequately protect engines without sacrificing fuel economy will become increasingly important.

Curious about emission requirements? Check out our post detailing further diesel engine emission regulations.


To learn more about PC-11 and how tightening environmental regulations will likely affect diesel engine maintenance facilities, or to discuss the requirements of a specific diesel engine model, contact Highway and Heavy Parts (HHP) at 844-304-7688 and speak with one of our ASE Certified Technicians. Or, you can always request a quote online!

Originally Posted December 26, 2013; Edited January 31, 2020