Terms of the Trade: What is Penetrating Oil?

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Penetrating fluids are low viscosity oils popular for lubricating squeaky hinges or loosening rusted fasteners like nuts and bolts. The name refers to the oil's ability to penetrate the microscopic spaces between threads.

In some cases, penetrating oils can be used as cleaners to clear away metal corrosion or remove sticky residues. Although they're good for a quick fix, they're not great for use as lubricants over the long run, since they tend to evaporate quickly.