Description Mobil Delvac 1220, 1230, 1240, and 1250 are heavy duty, diesel engine oils formulated from high performance base oils and a balanced additive system of ashless dispersants, metallic detergents, and inhibitors to control oxidation, wear, corrosion, and rust. They are used in a wide range of applications where a monograde lubricant is recommended including 2-cycle diesel applications (e.g. the Detroit Diesel’s Series 53, 71, 92, and 149 twocycle engines).