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In other words, the choice of viscosity would be different depending on whether you are living in Finland (0W/ 5W-30) or Nigeria (5W/10W/15W40 or even 20W50). Multigrade oils such as SAE 5W-30 and 10W-40 are widely used because, under all but extremely hot or cold conditions, they are thin enough to flow at low temperatures and thick enough to perform satisfactorily at high temperatures. The number after the W describes how thick the oil is at the engine’s normal operating temperature. The lower the number, the thinner the oil and the better the oil’s cold temperature/ cold start performance. In a 5W-30 for example, the number before the W describes the viscosity of the oil at low temperatures. This is why you would see something like this on the label: SAE 5W-30. Because the viscosity of oil changes with temperature, multigrade oils were developed to provide protection across a range of temperatures.
#OIL VISCOSITY CODE#
The long answer:The Society of Automotive Engineers (SAE) has established a numerical code system for grading motor oils according to their viscosity characteristics. The short answer:The numbers represent the viscosity of the oil and the W stands for WINTER. Probably the most important property of oil lubricant is the absolute viscosity, which is a measure of the force required to move one layer of the oil film. That’s what car service centres and mechanics are there for right?īut what if you find yourself in a position where you need to buy and put in the oil yourself? How do you know which oil to use and how do you read the label? What does SAE 5W-30 mean? In fact, most of us don’t even know what is under the hood of our car, let alone the type of oil that is in our engine. Classification according to the API degree: Light crude oil: API gravity higher than 31. Crude oils viscosity can vary from a low-viscosity liquid to up to tar-like, nearly solid form. Not all of us get to service our own cars. Both a crude oils viscosity and its API (American Petroleum Institute) degree are important parameters for classification.