ASTM D2422 Standard Classification of Industrial Fluid Lubricants by Viscosity System
4. Basis of Classification
4.1 Twenty viscosity grades are given in Table 1.
4.2 Each grade shall be designated by its nominal viscosity at 40°C.
4.3 The permissible variance in viscosity of each grade shall be as shown in the two right-hand columns of Table 1. These limits are based upon a +/-10 % deviation from the mathematical values which were used as the basis of construction of this system.
4.4 The lubricant supplier may choose to exert a manufacturing control on a given product that is closer than this +/-10 % tolerance. It is to be understood that any different percentage variation that he uses will still guarantee maximum and minimum values that are not outside the limits of the standard viscosity grade limits. However, the lubricant purchaser or the equipment designer shall not normally specify control closer than the maximum and minimums established herein for a given grade. Any exception to this rule shall be handled outside the scope of this system and on a direct consumer-supplier relationship.
