How to Test Oil Viscosity

Written by mark fitzpatrick | 13/05/2017
How to Test Oil Viscosity
There are a number of scientific ways of measuring the viscosity level of oils. (oil s image by Andrey Kiselev from

Viscosity is an important aspect for oil used in machines and transportation vehicles. Viscosity is defined as how the oil flows as a result of gravity. Viscous fluids help lubricate machines as their internal parts move. In the case of motor vehicle engines, viscous oil helps lubricate engine parts from overheating and welding together. Motor oil companies advertise how viscous their motor oil fluid might be with grades and data listed on the bottle. Consumers can test the viscosity of the motor oil themselves.

Fill a tub or container with water. The container needs to be filled enough so it can submerge an object. Be careful not to overfill the container, since it needs to be raised to a boiling temperature.

Warm the water to around 100 degrees Celsius. An external heat source is needed to heat the water. Position the container over the heat source and check the temperature of the water with a thermometer. Once the water reaches approximately 100 degree Celsius, maintain the temperature throughout the measurement.

Submerge the U-shaped glass tube in the water. Only allow the bottom U-bend into the water. Both ends of the tubes need to be exposed to the air. Make sure you can clearly see the glass tube and there is a calibrated region to the tube.

Tightly shut one of the tube ends on the glass tube.

Pour the motor oil into the open end of the U-shaped glass tube.

Time the stop watch immediately. The heat from the water should cause the oil to heat up and rise toward the closed end of the tube.

Record the time the oil rises to the calibrated region of the tube and then falls. To have the oil begin falling, remove the closed top of the tube and the oil should fall at a certain rate. The faster the oil rises and then falls, the more viscous the oil.

Things you need

  • U-shaped glass tube
  • Tub or container
  • Water
  • Heat source
  • Thermometer
  • Stopwatch

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