Viscosity is a property of liquids that describes their resistance to flow. It is sometimes referred to as “thickness” or “internal friction”. The viscosity of a liquid determines how easily it can flow, with a low-viscosity liquid flowing more easily than a high-viscosity liquid.
In the context of lubricants such as transmission fluid, viscosity is an important characteristic that affects the fluid’s ability to lubricate moving parts in the transmission and provide sufficient fluid pressure to maintain proper transmission operation. Viscosity is typically expressed in terms of centistokes (cSt) or Saybolt Universal Seconds (SUS), and is measured at a specific temperature.
Different types of transmission fluids have different viscosities, and it is important to use the correct type of fluid for your vehicle to ensure proper operation and longevity of the transmission. Some transmission fluids are formulated with a multi-viscosity rating, meaning that they maintain their viscosity over a range of temperatures, providing improved protection for the transmission in a wider range of operating conditions.