A viscosity measurement apparatus for measuring viscosity of a fluid under known pressure. A tube of known diameter and length allows the fluid to pass therethrough. A closed chamber is in fluid communication with the tube. A piston, sealably engaged with the chamber, may be moved by force of the fluid passing through the tube. A linear gauge measures the time required to move the piston. A mechanism is provided to reset the piston by forcing fluid back through the tube to empty the chamber to begin another measurement.