Royal Purple Duralec Super motor oil is a high-performance engine oil made for emissions-controlled diesel engines utilizing emissions equipment such as: DPF's, Catalytic Converters, EGR, and SCR injection. Royal Purple Duralec Super is an API CK-4 engine oil. Royal Purple Duralec Super motor oil is specifically formulated to maximize component life, extend drain intervals, and improve fuel performance. These premium lubricant formulations provide excellent high temperature resistance and low temperature pumpability, outstanding soot dispersancy, improved rust and corrosion protections, and prevention of varnish and sludge formation.