The variable commonly used to represent viscosity is the Greek letter 'eta' ( η). It may look intimidating at first, because it has some Greek letters in it, but don't let that scare you. The equation (Equation 1) shows you how to calculate the viscosity from your measurements. In order to calculate the viscosity, you'll have to measure the time it takes the sphere to fall, the distance the sphere falls, and the density of the sphere and the fluid. You can make your comparisons using the measured time for the sphere to fall, or you can take your project a little further and actually calculate the viscosity. You will release a sphere (glass marble or steel ball bearing) at the surface of the liquid and time how long it takes for the sphere to fall to the bottom of the beaker or cylinder. Instead of using fancy glassware, you can use a Pyrex beaker or graduated cylinder. Ostwald-type viscometer for measuring viscosity of liquids. Because viscometers are expensive (more than $170), you'll use a slightly different technique for this experiment.įigure 1. To measure viscosity at different temperatures, the viscometer is placed in a water bath. The higher the viscosity, the longer it will take the fluid to drain through the tube. The suction is removed, and the time it takes for the fluid to drain out is measured. Fluid is drawn up from the cup on the lower left into the tube on the right, using a suction bulb. Viscosity of liquids can be measured with a special piece of glassware called a viscometer (see Figure 1). For an engine lubricant, it is important that the viscosity does not change significantly as the temperature increases. Cooking oil has a higher viscosity-it pours more slowly than water. Water is an example of a fluid with low viscosity-it pours easily and quickly. The viscosity of a fluid is a measure of the fluid's resistance to flow. One way of measuring an oil's ability to lubricate is to measure its viscosity. The oil must be able to keep the piston moving smoothly at cold temperatures (when the engine first starts up) and also at the normally high operating temperature of the cylinders. Lubricate over a wide temperature range.' (Thibault, 2001).Seal piston and liner for optimum engine efficiency.

Lubricate engine moving parts to reduce friction and prevent wear.Without oil, the piston would not be able to move in the cylinder-the engine would seize up and be ruined. The oil is a lubricant-a slippery liquid that allows the piston to slide freely within the cylinder. In order to keep the pistons moving smoothly in the cylinders, there is a thin film of motor oil between the piston rings and the cylinder wall. The internal combustion engine that powers your family's car has moving parts that work at high temperatures for billions of cycles over its lifetime.

Viscosity of oil test