Viscosity Number
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A method of classifying an oil by number, based on its resistance to flow at a high temperature.
These numbers are usually prefixed by SAE which is the abbreviation for the Society of Automotive Engineers.
A lower SAE Number (i.e. SAE 5W) indicates a thinner oil with a higher flow rate, for use at lower temperatures.
A higher SAE Number (i.e. SAE 30) indicates a thicker oil with a slower flow rate, for use at higher temperatures.