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Eric, Automotive Repair Shop Manager
Category: Car
Satisfied Customers: 31899
Experience:  Automotive Repair Shop Manager, Technician/JA Mentor
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Austin Metro: Why does engine oil become black in colour with

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Why does engine oil become black in colour with time ?

There are a number of reasons for the oil turning black over time - engines all have some blowby past the piston rings and the gases contain carbon particles which become suspended in the oil, thus darkening the oil. The detergents in oil clean grime, carbon, and other particles from the internal engine parts, all of which wind up suspened in the oil, which darkens it. Over time, enough particles are in the oil to turn it a black color.

This is quite normal in a combustion engine

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