Abstract: A method of recovering crude oil for subsequent processing. The method contemplates the step of exposing the source of crude oil such as a subterranean petroleum reservoir or a vessel or container of tar sands, kerogen or the like to aliphatic or carboxylic acid, preferably oleic acid, to produce a solvated crude oil mixture of reduced viscosity. This mixture is saponifyed by reacting it with a nucleophilic base, preferably a hydroxide of potassium or sodium, under pressure whereby to separate the solvated mixture into petroleum crude and an acid soap which migrates to an aqueous phase. The petroleum crude is separated from the aqueous soap through conventional techniques. Afterwards, a desaponification step contemplates recovery of the aliphatic or carboxylic acid for subsequent recycling in the previously mentioned exposing step.