Citgo Citgard 600 15W40 Heavy Duty Motor Oil is made for use with engines using on road diesel. The superior technology protects current and older model low emissions engines equipped with exhaust after treatment systems. It exceeds the API CK-4 heavy duty requirements and has state of the art wear control technology for reduced wear. It provides advanced soot control and exceptional oxidation and thermal protection for operating at extreme temperatures. It is recommended for use in heavy duty commercial trucks, agricultural equipment, construction equipment and other diesel fueled engine applications.