Technical reference for ISO VG 68 hydraulic oil, covering operating conditions, typical applications, and specification requirements.
Operating context
ISO VG 68 hydraulic oil is a higher-viscosity, mineral-base hydraulic fluid used in systems operating under sustained load, higher operating temperatures, or where internal clearances are larger. It is commonly selected for industrial and mobile hydraulic equipment operating in warm environments or under continuous duty conditions.
The viscosity grade is defined by ISO 3448 and corresponds to a nominal kinematic viscosity of 68 mm²/s at 40°C.
Typical equipment use
This viscosity grade is generally specified for hydraulic systems where increased oil film thickness is required to support load-carrying capacity and component separation.
- Industrial hydraulic power units
- Presses, forming equipment, and heavy-duty machinery
- Injection moulding and production plant
- Mobile and off-highway equipment operating in warm conditions
- Hydraulic systems within waste, recycling, and bulk-handling plant
Viscosity behaviour in service
The higher viscosity of ISO VG 68 provides increased film strength under load and supports stable operation at elevated temperatures. This makes it suitable for systems exposed to sustained pressure, continuous operation, or higher ambient temperatures.
At lower temperatures, higher viscosity increases resistance to flow. For this reason, ISO VG 68 should only be used where specified or permitted by the equipment manufacturer, particularly where cold-start conditions apply.
Specification requirements
ISO VG 68 hydraulic oils are formulated to meet defined performance standards. The required specification is determined by system design, operating pressure, temperature range, and duty cycle.
- ISO 11158 HM for standard anti-wear hydraulic systems
- DIN 51524 Part 2 HLP for mineral-base anti-wear systems
- ISO 11158 HV where viscosity–temperature stability is required
- DIN 51524 Part 3 HVLP for systems exposed to temperature variation
Operating environment considerations
ISO VG 68 is commonly used in industrial and mobile applications where operating temperatures remain moderate to high and equipment operates under sustained load. In demanding environments, such as waste and recycling facilities, contamination control and specification discipline are critical to maintaining hydraulic system reliability.
Where multiple hydraulic oil grades are present on site, clear identification of ISO VG 68 systems supports correct oil use and reduces the likelihood of misapplication.
Compatibility and grade control
ISO VG 68 should only be replaced with another viscosity grade where substitution is permitted by the equipment manufacturer. Using lower-viscosity oils may reduce load-carrying capability, while higher-viscosity oils may affect system response.
When changing suppliers or specifications, compatibility with seals and residual oil should be confirmed, to avoid unintended system effects.
Product availability
Sinopec Online supplies ISO VG 68 hydraulic oils formulated to recognised international standards for industrial and mobile hydraulic systems.
All Sinopec lubricants supplied by Sinopec Online are genuine, factory-sealed products, backed by technical support.
Technical support
For product selection support, contact Sinopec Online or call +44 020 8068 3444.