Hydraulic oil labels such as "HLP 46" look like code. They are actually a short description of the oil type and its viscosity grade, based on the ISO 6743-4 classification and DIN 51524 requirements.
What HL, HLP and HVLP mean
- HL – refined mineral oil with rust and oxidation inhibitors, for lightly loaded systems.
- HLP – HL plus anti-wear additives. This is the most common type for industrial pumps and presses.
- HVLP – an HLP oil with a high viscosity index, so viscosity changes less between cold start and hot running. Useful for mobile equipment and outdoor machines.
What the number means
The number is the ISO VG viscosity grade, the oil's viscosity in centistokes at 40 °C. ISO VG 32, 46 and 68 are the most common. Higher numbers mean thicker oil, which suits higher temperatures or loose clearances.
How to choose
- Find the ISO VG grade in the machine manual.
- Use HLP for vane, gear and piston pumps working at medium or high pressure.
- Choose HVLP when ambient or working temperature varies widely.
- Never mix different types without flushing the system as advised by the OEM.
Keep hydraulic oil healthy
Most hydraulic failures are caused by contamination. Keep breathers and filters in good order, avoid water ingress and use oil analysis to decide change intervals.
Need help choosing?
Share your machine make and model, operating conditions and the manufacturer's recommendation. The RJ Enterprises technical team will suggest a suitable product and quote bulk pricing across India. Request a quote or call us.
