Dark oil is not automatically “bad” oil
Engine oil can darken during normal operation as it carries contaminants and does its job. Colour alone cannot reliably tell you whether the oil is due for replacement.
What appearance can tell you
Amber
Often associated with relatively fresh oil, but time and mileage still matter.
Often associated with relatively fresh oil, but time and mileage still matter.
Dark brown / black
Can be normal. Do not change oil based on colour alone.
Can be normal. Do not change oil based on colour alone.
Milky
Can indicate moisture or another issue and deserves attention.
Can indicate moisture or another issue and deserves attention.
Gritty / particles
Unusual texture is a reason to have it checked.
Unusual texture is a reason to have it checked.
Better indicators
- Owner’s manual and manufacturer interval
- Mileage and elapsed time
- Oil type
- Driving conditions, including short trips and severe use
- Vehicle oil-life monitoring system, when equipped
References: your vehicle manufacturer maintenance schedule and AAA automotive maintenance guidance. Colour illustrations are educational only and are not a diagnosis.