MobilPlus Elite Full Synthetic Heavy-Duty Motor Oil SAE 15W-40 is formulated with synthetic base oils and a premium additive package. This oil is designed for use in for use in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway and Tier 4 non-road exhaust emission standards as well as for previous model year diesel engines. This oil is especially effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used. Texas Fortis Elite Full Synthetic Heavy-Duty Diesel Engine Oils API Service CK-4/SN provide 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 API CK-4, this oil exceed the performance criteria of CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4 and can effectively lubricate engines calling for those API Service Categories. When using this product in conjunction with fuel containing higher than 15 ppm of sulfur, consult the engine manufacturer for service interval recommendations.