Sludge can block your engine's vital oilways like cholesterol and if untreated, can rob an engine of its power and ultimately its life. Castrol GTX is a premium conventional motor oil that has been helping to extend engine life for over 50 years. It has evolved to meet the needs of consumers and vehicle manufacturers since 1968 and continues to innovate and remain a trusted brand today. Severe driving conditions such as heavy traffic, poor fuel quality, harsh driving conditions and exceeding oil change intervals can all cause the build-up of a thick, tar like substance called sludge. If untreated, it can rob a car's engine of its power and ultimately its life. GTX is specially engineered to prevent harmful build-up of sludge while protecting against new oil splatter formation better than tough industry standards. Help Extend the Life of Your Engine with Castrol GTX.