What happens if the oil turns black or dark in color in the car?

The cleaning of the internal organs of the engine is one of the lubricant’s functions, so it must necessarily darken with the passage of time. If the oil turns dark it isn't bad. It is one of the functions of lubricants to keep the engine clean, so it is normal for the lubricant to turn darker as it is used.

Related questions:

• The oil has turned black, does that mean I have to change it?
• If the oil turns dark, is it bad?
• What happens if we have a dirty lubricant?