Mobil Delvac™ HDEO 15W-40 and 10W-30 are synthetic blend diesel engine oils designed to meet warranty requirements for high-speed, four-stroke heavy duty diesel engines. Mobil Delvac™ HDEO 15W-40 and 10W-30 are oils designed to meet warranty requirements for high-speed, four-stroke heavy duty diesel engines. These products are formulated to maintain the durability of emission control systems, including diesel particulate filters and other advanced aftertreatment systems and delivers an average up to 30% more wear protection versus CK-4 requirements. These products are formulated to maintain the durability of emission control systems, including diesel particulate filters and other advanced aftertreatment systems.