Saybolt Universal Second

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Saybolt Universal Second (Often SUS or SSU) is a measure of kinematic viscosity used in classical mechanics. It is the time that 60 cm³ of oil takes to flow through a calibrated tube at a controlled temperature. The SUS is used for oils with flowing time up to 600 seconds, in the range of low to medium viscosity such as machine oils.

When the flowing time surpasses 600 seconds, Saybolt Furol Second should be used instead of Saybolt Universal Second. The tube diameter in the two scales is such that the Furol viscosity is one-tenth of the Universal viscosity:

$Saybolt Furol Viscosity = \frac{Saybolt Universal Viscosity}{10}$