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15W-40

15W-40 is a very common viscosity grade for diesel engine oil. GTX Diesel is a 15W-40 diesel engine oil formulated to help extend engine life.

The right 15w-40 oil for your engine

If you need a 15W-40 diesel oil, Castrol GTX Essential  Diesel helps extend engine life, protecting against the wear and tear of severe weather, rough roads and heavy tows. As a 15W-40 viscosity grade, it flows like a 15 weight oil from start up in Winter, but provides the protection of a 40 weight once the engine reaches full operating temperature.