Does oil conduct electricity?
Engine oil is not a conductor, but due to the presence of additives and moisture it has a much lower breakdown voltage.
So you cannot pour engine oil into the transformer.
By the resistance of the oil, one can judge its performance and even the condition of the engine.
Oil is an organic substance that is not an electrolyte, which includes solutions and melts of salts, acids and alkalis. Motor oil is obtained from petroleum products and is a mixture of hydrocarbons, therefore motor oil is not an electrolyte, it does not dissolve in water.