Starting on December 1st, 2016, a new specification of diesel motor oil, API CK-4, will be available. Following extensive testing, Ford concluded that some CK-4 motor oils could potentially lead to high mileage engine wear in Ford diesel engines.
In response, Ford has developed its own specification of diesel motor oil – WSS-M2C171-F1. This new specification of diesel motor oil has been designed for use in all Ford diesel engines and will be available in early 2017. Until WSS-M2C171-F1 is available, though, Ford recommends only using diesel motor oils that show CJ-4 or CJ-4/SN on the label.