Modern driving conditions place increased demands on engines, resulting in the build-up of dirt and sludge that can clog key engine parts. If not completely removed during oil changes, these substances can impair engine operation. Driving in extreme conditions. For example, frequent short-distance driving, stop-and-go/heavy traffic driving, and driving on slopes. Castrol Engine Shampoo is a pre-oil change treatment that contains a powerful cleaning agent (PCA) that removes engine sludge* and envelops dirt particles, helping them to be eliminated and cleaning the engine ready for new oil. Castrol Engine Shampoo: contains Powerful Cleaning Agent (PCA) which helps remove sludge deposits from metal engine surfaces Castrol Engine Shampoo can be used whilst your car is awaiting service. There is.