Castrol RX Diesel 15W-40 is a premium quality mid-ash heavy duty diesel engine oil, great for plant, highway, off-road, and mixed fleet operations. RX DIesel contains cleaning agents to reduce harmful build-up on engines surfaces and pistons while also utilising anti-oxidant controls to prevent oil thickening over the service period to extended the life of your engine. This product can be used in turbocharged and naturally aspirated diesel engines requiring an oil meeting API CI-4 or earlier specification, and is particularly suitable for use in US engine technology pre ADR 80/02, such as Cummins, Mack, Caterpillar and Detroit Diesel (4-stroke) heavy duty diesel engines. Castrol RX Diesel 15W-40 is also suitable for use in diesel 4WDs and light commercial vehicles not fitted with DPFs (Diesel Particulate Filter) or DPDs (Diesel Particulate Diffuser). To find the oil type and viscosity suggested for your vehicle; either add your vehicle to My Garage or check with your manufacturer, vehicle user manual, your local mechanic or head in-store and talk to one of our friendly team.