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 and synthetic oils of the types API groups I, II, III, and IV used in hydraulic systems, where the performance requirements demand fluids with one of the following characteristics:

1.1.1 A refined base oil or synthetic base stock (Class HH),

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

1.1.3 A refined mineral base oil or synthetic base stock with rust and oxidation inhibitors plus anti-wear characteristics (Class HM),

1.1.4 A refined mineral base oil or synthetic base stock with rust and oxidation inhibitors, anti-wear characteristics, and increased viscosity index higher than 140 (Class HV),

1.1.5 A refined mineral base oil or synthetic base stock with rust and oxidation inhibitors plus anti-wear characteristics meeting a higher performance level than an HM fluid to address higher demanding hydraulic systems (Class HMHP), and

1.1.6 A refined mineral base oil with rust or synthetic base stock and oxidation inhibitors, anti-wear characteristics, and increased viscosity index higher than 140 meeting a higher performance level than an HV fluid to address higher demanding hydraulic systems (Class HVHP).

1.2 This specification defines the requirements of mineral oil-based or synthetic-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.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5.1 Exception—In X1.3.9 on Wear Protection, the values of pump pressure are in MPa, and the psi follows in brackets as a reference point immediately recognized by a large part of the industry.

1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.