Solvent
Because non-polar solvents lack the polarity needed to form hydrogen bonds, they rely on the much weaker Van der Waals force, which is a weak attraction between molecules that occurs when they come very close together. When non-polar molecules, like those in oil, come close to other non-polar molecules, like those in grease, they experience these tiny attractions, allowing them to stick together. This is how oil can dissolve grease.