Castrol GTX is one of the worlds most trusted engine oils. It's more than just oil. Its liquid engineering that protects against problems, like sludge that your engines faces every day. Severe driving conditions such as heavy traffic, poor fuel quality, harsh weather conditions and exceeding oil change intervals can all cause the build up of a thick, tar-like substance called sludge. You cant see this sludge build-up but it can damage your engines performance and cause premature engine failure. Help extend the life of your engine with Castrol GTX.