Black - oils for diesel engines; white - oils for gasoline engines.
Since the ranges of application of seasonal oils of neighboring SAE classes overlap, short-term temperature changes can be ignored. It is allowed to mix oils of different viscosity grades if topping up of oil is required, and the ambient temperature no longer corresponds to the viscosity grade of the oil filled into the engine.
Additives - no matter what kind - should not be mixed into either oil or fuel.