In a solution of oil and gasoline, the most important interaction is Van der Waals forces. Van der Waals forces are weak intermolecular forces that include dipole-dipole interactions, London dispersion forces, and hydrogen bonding. In the case of oil and gasoline, the molecules are nonpolar, so London dispersion forces are the dominant type of Van der Waals force. London dispersion forces arise from the temporary fluctuations in the electron clouds of molecules, creating instantaneous dipoles. These instantaneous dipoles can then induce dipoles in neighboring molecules, resulting in weak attractive forces. The sum of these attractive forces between the oil and gasoline molecules is what holds the solution together.