Vinegar is a sour liquid made up of acetic acid compounds. Oil is a complex non-polar chemical compound with a high amount of hydrogen and carbon in its structure.
Vinegar is a polar acid, although a weak one.
Generally, for a substance to mix with another one, they must be similar.
Solubility of compounds controls miscibility.
When two substances are miscible, they can be said to be soluble in one another.
In solubility, like substances dissolves like substances.
This implies that polar compounds will only dissolve polar compounds.
Non-polar compounds will only dissolve in non-polar solvents.
Since vinegar is polar and oil is non-polar, they will not dissolve one another.
