This specification covers the standard for mineral oils used in hydraulic systems which require refined base oil (Class HH), refined mineral base oil with rust and oxidation inhibitors (Class HL) or refined mineral base oil with rust and oxidation inhibitors plus antiwear characteristics (Class HM). This specification only covers lubricating oils before they are installed in the hydraulic system and does not include all hydraulic oils. Requirements for the mineral oils shall include, but not limited to, viscosity, specific gravity, appearance, flash point, chemical acid number, corrosion, water separation, elastomer compatibility, air release, and thermal stability.

1.1 This specification covers mineral oils used in hydraulic systems, where the performance requirements demand fluids with one of the following characteristics:

1.1.1 A refined base oil (Class HH),

1.1.2 A refined mineral base oil with rust and oxidation inhibitors (Class HL), and

1.1.3 A refined mineral base oil with rust and oxidation inhibitors plus antiwear characteristics (Class HM).

1.2 This specification defines the requirements of mineral oil-based hydraulic fluids that are compatible with most existing machinery components when there is adequate maintenance.

1.3 This specification defines only new lubricating oils before they are installed in the hydraulic system.

1.4 This specification defines specific types of hydraulic oils. It does not include all hydraulic oils. Some oils that are not included may be satisfactory for certain hydraulic applications. Certain equipment or conditions of use may permit or require a wider or narrower range of characteristics than those described herein.

The following safety hazard caveat pertains to the test methods referenced in this specification. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitation prior to use.