Shield X Synthetic Blend Heavy-Duty Engine Oil, SAE 20W-50, API CJ-4/SN parasynthetic crankcase lubricants for use in modern diesel engines. Formulated with a blend of synthetic and conventional base oil as well as a premium quality additive package, this oil exhibits excellent detergent, dispersant, anti-wear, anti-corrosion, anti-oxidant, and anti-foaming properties.