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Which of the New Diesel Engine Oils Do You Need?

Earlier this year, the American Petroleum Institute (API) approved two new diesel engine oil standards, API Service Categories CK-4 and FA-4. These new categories resulted from several years of collaborating between engine manufacturers, oil marketers, and additive suppliers. When the categories launch on December 1, 2016, it will be the first time since 1994 that there will be two different diesel engine oil categories, says Kevin Ferrick of API.

The new engine oil standards have been developed to protect engines, meet new government regulations, and ensure engine oil performance, he adds. “The new service categories improve upon existing standards by providing enhanced protection against oil oxidation and protection against engine wear, particulate filter blocking, piston deposits, and degradation of low- and high-temperature properties,” Ferrick points out.

API CK-4 oils will replace current API CJ-4 engine oils and will be backward-compatible with current diesel vehicles and will feature improved shear stability, oxidation resistance, and aeration control, Ferrick explains. API CK-4 oils will have similar viscosity grades to current API CJ-4 oils. “They have been created to easily replace oils used with current engine technologies and will have a minimum high-temperature, high-shear (HTHS) viscosity,” he adds.

New API FA-4 oils will include lower viscosity grades to meet the needs of next-generation diesel engines built beginning in 2017, Ferrick explains. “They are intended to help increase fuel economy while providing strong engine protection. These oils will have limited backward compatibility because some older engines were not designed to operate with lower viscosity grades. API FA-4 oils were intentionally named FA-4 to prevent their confusion with CK-4 oils, but FA-4 oils have to provide the same level of protection except with a lower HTHS viscosity,” he details. “Engines designed to operate at the lower HTHS viscosity may see a fuel economy benefit compared with oils having higher HTHS viscosities.”

API has introduced a special Service Symbol Donut to help technicians and consumers easily identify the API FA-4 diesel engine oil and distinguish it from CK-4 oils. The new API FA-4 donut features a shaded section, and the API CK-4 Service Symbol Donut will look the same as the current CJ-4 Donut.

To find out if you need either the new CK-4 or FA-4 lubricants, check with your owner’s manual, your engine manufacturer, or go to


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