Viscosity is the internal friction of fluids, the resistance of one fluid layer to sliding over adjacent layers. Viscosity makes lubrication possible. Viscosity allows the movement of one loaded surface over another to drag a lubricant between them, where it begins to carry at least some of the load, thereby making sliding easier. Dip your fingers in water and rub fingertips together and you feel considerable friction. Water has a low viscosity, so the pressure of your fingers quickly squeezes it out from between them. Put a drop of oil on one fingertip—cooking oil from the kitchen cruet will do—and rub again. Big difference. The greater viscosity of the oil (about 60 times that of water), combined with the motion of your fingertips, drags oil between their surfaces. This, by supporting part of the pressure on low-friction liquid films, greatly reduces the friction you feel.