Castrol RX Diesel 15W-40 CI-4/E7 is a multi-purpose, heavy duty diesel engine oil. It is suitable for use in high speed 4-stroke diesel engines that use a broad range of fuel qualities. It is also compatible with diesel engines fitted with exhaust gas recirculation (EGR) systems. FEATURES AND BENEFITS: Contains cleaning agents which displace particles that may otherwise build up on your engine surfaces reducing deposits.Contains anti-oxidants which disrupt the chemical reactions that can lead to oil thickening.Provides effective piston deposit control and maintains its viscosity to encourage long and healthy engine life.