International standards are used in lubricant documentation to provide consistent classification, test reference, and terminology across manufacturers, industries, and regions. This page explains the ISO and DIN standards most commonly cited in industrial lubricant specifications and how they are interpreted in technical literature.

These standards define measured properties and classification frameworks. They do not determine application suitability, service intervals, or equipment approval, which remain the responsibility of the equipment manufacturer.

ISO viscosity grade system (ISO VG)

The ISO viscosity grade system classifies industrial lubricants by their kinematic viscosity measured at 40 °C, in accordance with ISO 3448. Each ISO VG number represents a nominal viscosity value with defined upper and lower tolerance limits.

For example, an ISO VG 46 lubricant has a kinematic viscosity of approximately 46 mm²/s at 40 °C, within a specified tolerance band. Adjacent grades are spaced to minimise overlap and reduce the risk of misapplication.

ISO VG classifications are widely used for hydraulic oils, circulating oils, gear oils, and other industrial lubricants where viscosity selection is critical to pump efficiency, component protection, and temperature control.

DIN lubricant classifications

DIN standards provide classification systems and terminology commonly used in European lubricant documentation. These standards describe lubricant type, base oil category, additive presence, and intended operating characteristics through structured codes.

DIN classifications often appear alongside ISO viscosity grades to provide additional context. For example, a DIN code may indicate whether a hydraulic oil contains anti-wear additives, corrosion inhibitors, or oxidation stabilisers.

DIN standards reference test methods and performance descriptors but do not imply equipment approval unless explicitly stated by the equipment manufacturer.

How ISO and DIN references are used in practice

• To specify viscosity class and allowable tolerance range
• To reference standardised test methods and measurement conditions
• To provide consistent terminology across technical data sheets and manuals
• To support comparison of lubricants within the same classification framework

Standards references should always be read in conjunction with the original equipment manufacturer’s service documentation and operating guidelines.