Wolf's Head Extreme-Duty Synthetic Blend CK-4/SN 15W-40 is premium high performance diesel engine oil utilizing the latest in engine oil additive technology to offer the ultimate protection of your engine. Designed to meet or exceed the latest OEM and API CK-4 requirements, it is also backwards compatible to previous OEM and API specifications such as CJ-4, CI-4, CI-4+, and CH-4. Wolf's Head CK-4/SN 15W-40 carries the API SN classification for use in gasoline engines and is an excellent choice for operators with mixed fleets. This oil is specially designed to protect EGR/Low-Emission Diesel Engines while maximizing the durability of Diesel Particulate Filters (DPF's).