Viskositetsklass

Viskositetsklass is a term used in Swedish industry to describe the viscosity class of liquids. It refers to a standardized categorization of a fluid’s flow resistance at a defined temperature, enabling comparison and specification across products and processes. The classification is usually based on either dynamic viscosity (measured in milliPascal-seconds, mPa·s) or kinematic viscosity (mm²/s, commonly referred to as centistokes, cSt). The choice of testing temperature and measurement method is defined by relevant standards, such as ASTM D445 or EN ISO 3104. In many contexts, viscosity is expressed at 40°C or 25°C, and for lubricants the ISO viscosity grade (ISO VG) or SAE grades are commonly used. ISO VG numbers, such as 32, 46, 68, indicate approximate kinematic viscosity at 40°C, within specified tolerances.

Viskositetsklass is applied across sectors: lubricants (motor oils, gear oils, hydraulic fluids), paints and coatings, fuels, and process liquids. In procurement and product data sheets, the class helps selecting fluids that will pour, lubricate, or coat as required in a given temperature range; it also informs storage and handling. Because viscosity is strongly temperature-dependent, the same liquid can belong to different classes at different temperatures, and actual performance depends on shear conditions and temperature during use.

While the class provides a concise specification, it does not fully determine performance, which also depends on factors such as volatility, oxidation stability, and additive package.