Is car oil supposed to be brown?

No, car oil is not supposed to be brown. Fresh, clean engine oil is typically amber or light brown in colour. However, as it circulates through the engine, it can darken and become a darker brown or black colour due to contaminants and debris, which is normal. If the oil is excessively dark, thick, or has a burnt smell, it may indicate a need for an oil change or potential issues with the engine.