How to Test Oil Viscosity

Oil viscosity - how oil flows as a result of gravity - is one of its most important properties. An oil with a higher viscosity will generally be thicker and take a longer time to succumb to gravity. One of the main functions of oil is as a lubricant in machinery or vehicles - t prevents them from overheating, and as a result, becoming welded together. Since the viscosity of an oil will affect how efficiently it can achieve this objective, users must be aware of an oil’s viscosity before using it. Manufacturers provide this information by placing grades or data on the bottle itself.

An Oil’s viscosity can be determined in a laboratory or even at home. Here is how:

Testing Oil Viscosity at Home

The process is a complicated and potentially dangerous one, and so should not be undertaken without extreme care and the correct equipment and safety measures:

1. Fill a container with water and boil to 100°. The water should be deep enough to submerge an object, but not overfilled so that it will spill. Maintain the temperature throughout the test.
2. Submerge an open-ended U-shaped glass tube in the water, so that the bend is submerged, but the ends are open to the air.
3. Seal one of the ends of the tube.
4. Pour the oil into the open end.
5. Using a stopwatch, record how long it takes for the heated water to raise the oil’s temperature enough that it rises to the sealed end of the tube. When it reaches the end, remove the seal and record how long it takes to fall.
6. The longer it takes for the oil to rise and fall, the more viscous the oil.

Testing Oil Viscosity in the Lab

The above process is a difficult and unreliable one, and to achieve a more dependable figure, testing in a laboratory is advisable. The two main methods of oil testing in a laboratory are the capillary tube viscometer method, which measures kinematic viscosity, and the rotary viscometer method, which measures absolute viscosity. In layman’s terms, the former measures how quickly the oil will flow, whilst the latter determines how easily it can be stirred. The former is much more prevalent in terms of measuring an oil’s viscosity.

Over the years viscometers have become more and more sophisticated. To see an example of one such exciting development, read the article, Viscosity Index Analyser for Optimal and Cost-Effective Refining Operations, which talks about the advantages of a new product released earlier this year.