To be more specific, it is the thickness of oil at a given temperature. Commonly, though, we think of it as an oil’s thickness. Technically, viscosity is defined as resistance to flow. We tend to choose an oil with a viscosity that we believe is correct for our particular engine, but would another viscosity improve or reduce the life of the engine? Can we pick and choose a viscosity outside the manufacturer’s recommendations? Most of us have only a vague understanding of viscosity.
