U1P-Duty SAE 5W-40 Full Synthetic Heavy-Duty Motor Oil, API CK-4/SN, is formulated with synthetic base oils and a premium additive package. This oil is designed for use in high-speed, four-stroke cycle diesel engines that meet 2017 model year on-highway and Tier 4 non-road exhaust emission standards, as well as in previous model year diesel engines. It is especially effective at sustaining emission control system durability where particulate filters and other advanced after-treatment systems are used. U1P-Duty SAE 5W-40 Full Synthetic Heavy-Duty Motor Oil, API CK-4/SN, provides enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration, as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase. In addition to meeting API CK-4, this oil exceeds the performance criteria of CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4, and can effectively lubricate engines requiring these API service categories. When using this product with fuel containing more than 15 ppm sulfur, consult the engine manufacturer for service interval recommendations.